Optimal Orientation For Solar Panels In Australian Capitals: Directly North Isn’t Always Best
It is generally accepted the best direction to face solar panels to get the maximum possible output is directly north. While this is not a bad direction, it is often possible to get a very small boost by having them face slightly away from due north. Usually facing them a little to the east will improve output, but in some locations a small nudge to the west is best.
While it doesn’t make much difference, the misapprehension that due north is always best is very common and if you believed it yourself up until now, don’t worry, it’s not your fault. It’s the fault of the Germans. Or at least that’s who I’m blaming. In every location in Germany I’ve looked at due south always seems best and when solar took off Down Under this may have led people to believe due north would always be best here.1
There are two reasons why a direction other than true north can be a little bit better:
- Lower average temperature in the morning can cause solar panels to operate more efficiently than in the afternoon, giving those that face a little to the east a slight advantage.
- Average cloud cover can be consistently greater during certain times of day. This is often in the afternoon which gives a slight disadvantage to panels that face west, but in some places it can be the other way around.
There are definitely good reasons for not facing solar panels in the direction of maximum possible output. A household can increase their self consumption of solar electricity by positioning panels so they’ll produce less energy overall, but more during periods when electricity use is high. Also, if feed-in tariffs based on either wholesale electricity prices or the time of day become popular — or compulsory — then maximizing the feed-in tariff received could make more economic sense for a household than maximizing total output.
But maximizing output is often the best choice at the moment. This is especially true for larger systems where the extra feed-in tariff received from the extra output will often outweigh any benefit from increasing solar self-consumption. It is also the best choice for the environment as the greater output will displace more fossil fuel generation. For this reason, if you’re not sure what’s the best direction to face your panels, I say go for maximum output.
Of course, most people don’t get to decide which direction they face their solar panels. It’s determined by the shape of their roof. So to help people decide what is the best direction to face their panels, for all the Australian capitals I’ll describe:
- The direction in which panels will generate over 99.9% of maximum possible output.
- The range over which they will generate at least 99% of maximum possible output.
- The range over which they will generate at least 95%, 90%, and finally 85% of maximum possible output.
I will be using the PVWatts site to determine these values. This means I run the risk of being incorrect if their Australian database is off or doesn’t run its calculations correctly in. But it is made by the United States’ National Renewable Energy Laboratory, who are a pretty canny lot, and I feel confident their results will be at least close to correct.
A Matter Of Degrees
I will give you the results in degrees. By this I don’t mean I’ll tell you the results slowly or gradually. What I mean is I’ll give you them in the form of a circle’s 360 degrees where north is 0 degrees, east is 90 degrees, and west is 270 degrees. The image below shows how degrees and compass directions work:
Image: Wikipedia
I will also meticulously prepare highly informative and easy to understand graphics for you. Either that, or I’ll just dump the raw information on Finn and convince him to do it.2 Actually, that seems easiest now I think about it.
The Optimal Direction For Maximum Output!
If I put all my results into a table I get this:
But it will probably be much easier to follow the wonderful graphic Finn has made for each capital:
While due north isn’t quite perfect, it turns out to be pretty close, as panels facing that way will produce at least 99% of their maximum possible output in every capital except Darwin, where it will be just below that amount.
Darwin in the far north, where the sun is always high in the sky, offers the greatest flexibility in positioning panels for high output. Hobart in the far south is far worse, with output falling the fastest of all the capitals as panels are shifted away from their optimum position.
In four capitals — Adelaide, Brisbane, Canberra, and Darwin — solar panels will generate at least 85% of the maximum when facing directly east or directly west while Melbourne just barely fails to make it into this group.
The Worst Direction For Solar Panels
Now I’ve worked out the best direction, along with reasonable directions, I may as well work out the worst direction for each capital.
Below I’ve listed the worst direction solar panels can face for each capital — which is never very far from 180 degrees due south — and what percentage their annual output would be compared to facing the optimal direction. Because the output varies according to the slope of the roof I have assumed it will be 20 degrees, which is a nice round figure between the most common slopes of 15 and 22.5 degrees. The results for both of these roof slopes will be very close to the figures below:
- Adelaide: 184 degrees 74%
- Brisbane: 177 degrees 71%
- Canberra: 178 degrees 72%
- Darwin: 199 degrees 83%
- Hobart: 193 degrees 66%
- Melbourne: 186 degrees 71%
- Perth: 194 degrees 73%
- Sydney: 187 degrees 72%
In a typical capital you can expect solar panels facing the worst direction to produce around 28% less energy than those facing the best. The standouts are Darwin with only a 17% reduction and Hobart where total output is reduced by 33%.
Given the very rapid payback of north facing solar power, which is even better than when I wrote this article on it, south facing solar can definitely pay for itself for many households. So whether you have no choice because of the shape of your roof or because you want your roof to produce the most solar energy possible, south facing panels can be a viable option.
South Facing Solar Can Suck In Winter
One thing to note is south facing solar produces much more output in summer than winter. In Sydney, typical south facing solar panels will produce over 5 times more energy in December than June, while in Hobart the difference between those months will be more than 10 to 1. This means a household’s self consumption of solar energy from south facing panels is likely to be much less than from panels facing other directions, which is a consideration when deciding to install them.
Footnotes
- I even consulted with Dr Inga Rachelle Ernst and she agreed with me. Ernst is an actor turned film maker and environmental activist from Germany who has directed a number of environmental documentaries including Die Gutt Erde, Eine Unbequeme Wahrheit, and Extremer Naturalismus Siebenundzwanzig. ↩
- Finn! I’m too stupid to do vectors! Will you make my gwaphics for me? Pwease? Pwetty pwease? ↩
About Ronald Brakels
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Unless you are building a new house then applying this theory is going to very difficult or near impossible on existing house that faces North. Would be better to make your Solar panels track and follow the sun.
Not just about installing on existing houses.
Think about us out on farms and construction sites where the PV panel on a remote security camera or irrigation pump, or on a remote area site office can be oriented in any direction – that’s my use for this information.
This article is more useful to me than the lazy advice of local solar contractors who want to double the panel wattage and double battery storage “just in case” and have ZERO advice on optimum orientation and tilt other than “solar north and use latitude for tilt angle”.
Tim at Mornington Victoria. Present; 2014 had 16 Chinese solar panels installed by AGL/United Energy- They face east, north and west with Eko 4 Kw inverter. We clean panels 2x/yr. & use approx. 4 KW /day with no aircon. Changes to Feed in tarrif now almost zero Problem; June ‘23 Inverter ceased to function. Local inspection correctly pronounced inverter not powerful enough for poor solar supply due to part winter shade but since then found that one Panel has ‘crazed’. Have located Bundle sale @ under $8k for German panels however the removal of old panels, replaced with Bundle would represent 9 year’s Electrical supply. Is it worth it? Thank you
Hi Tim, Ronald here.
If your inverter has failed and your solar panels are failing, the best step to take is to replace the entire solar system with a new larger one. Even if you don’t have space on your roof for more than 16 panels, improvements in panel efficiency since 2014 mean you can fit a higher efficiency system in the same space.
You can get a good new system installed for less than $8,000. And if you find an installer through us we will back them up with our good installer guarantee:
https://www.solarquotes.com.au/installation-guarantee/
If you’d like us to put you in touch with some installers, then go to this page…
https://www.solarquotes.com.au/quote/start/
…and enter your postcode. Click on “Solar only” and then answer the questions that come up as best you can. If having a rapid payback time is important, say that you want a budget system when that question comes up. You will still receive a well installed and reliable system.
If you have any questions, please don’t hesitate to ask.
On this topic I found something really odd that I was not expecting.
I have many panels on 3 sides of my house. In fact I swapped out 21 panels from North to South when I upgraded the North panels.
In this summer past I found that the array on my South side produced higher peak production days than it did when the panels were on the North ( by 3 kWh ). For example the peak day for this array was nudging 34 kWh in mid summer 18 but in mid summer 19 it produced a number of days above 34 and up to 37kWh. Explain that please?
Footnotes.
The whole array was moved from North 12 deg to South 192 deg
I’m in Adelaide and there are no shade issues.
The array in question comprises 21 x 260W and a Bosch 4.6 inverter
It could be a case of in Adelaide them north facing panels are getting very hot and later in the day after 11 am the South panels are not cloud covered
Hmm, the peak days usually occurred on days under 35 deg anyway, usually the peak happens on a mild day the first or second of a streak of no cloud.
Hi Mark
That does seem odd. According to PVWatts in January, Adelaide’s sunniest month, your north facing panels should be producing 6.5% more per kilowatt than your south facing panels. It it possible there is dirt on your north facing array or potentially a problem with it. While it’s not summer anymore you could put the results for your north and south arrays into the solcaster site to see if they are behaving as expected:
https://solcast.com.au/rooftop-solar/free-pv-system-performance-estimation-tool/
Hi Ron
They are the same panels so it doesn’t matter what the North did or did not do this this summer. I moved the old North array to the South, yes I washed them before they were installed and you might say they were dirty the previous summer on the N – but no the 34kWh maximum day was in the year they were brand new,
The result must be related to the 12 degree angle, from North it was slightly East but South it’s slightly West?
Sorry, didn’t quite follow there. But according to PVWatts at least:
https://pvwatts.nrel.gov/
They should have been producing more in summer when they were facing north. I don’t really have any idea why they might be performing better now unless there was an issue that got fixed when they were moved.
Yeah that’s why I was so surprised, it was meant to be better on North. I mean it was for total year production by a long way, just not peak day generation in a window of about 3-4 weeks in January, I have all the numbers that back it up.
Hi – How has the last 3 years been with your system 0 is the Southern array still performing in the peak of summer??? (late afternoons that last light can be an AC saver.)
Good Article Ronald. I have built 2 systems on my properties in recent times: first off in Lismore, where the inverter is 10Kw, but output limited to 5Kw, with 3Kw of panels facing relatively East, on 15 deg pitch, & 10Kw on West side.
That system performs well, with viable energy to fairly late in the day. (No figures because the inverter is not on the web yet, but it has averaged 40Kw/day for over 2 years. My other system is at home, where I recently replaced the system. Here, I am on 2 phase, so have 2 of 5Kw Solar Edge inverters, with Optimisers due to the shading) with 14.5Kw total panels. 8Kw facing North on 22 deg tilts (new panels on the old racking), then about 7Kw facing west on 15 deg tilt. The best output from this system was 85Kw/day, but the average so far is about 45Kw. (Only installed in November, so no full annual output). This system is restricted to 8Kw by voltage rise.
So, what I am trying to point out is that there are other issues as well. I was surprised that the export limits do not greatly affect the system exports (in my case!). The peak generation is for such a short period, (say 3 hours) that the output is below the limit for most of the day. ´Overpowering´ the inverter is definitely worthwhile, but the rebate cuts out at 33 percent over.
My latest system should pay for itself in less than 4 years.
We put up an evacuated tube hot water system, if the woman in the office had bleated one more time is HAS to face north. I was going to ask True north or magnetic north?
Fitted to a roof facing 300 degrees, gets all the afternoon sun in winter, the best option for short days of winter. Windows face that way, heats the entire house…?
Of all tests I have done (in Victoria) I found West facing panels produced more output than East facing panels. I think it’s due to there being more fog/mist and other debris in the air in the mornings and by the afternoon it has all cleared.
And west facing panels will continue to power the aircon on hot summer afternoons, after the sun has slid off the north facing array. (I’ve just received building approval for an amendment to the plans for the off-grid build, to turn the planned western gable into a 40 degree pitched hipped roof. It’ll only fit 9 x 60-cell panels, so I’ll be looking for good ones. The north facing array can be 24 panels, but why discharge a battery when a supplementary array can do the work?)
Even if on-grid, self-powering aircon in the late afternoon would have to be a big plus.
In he overall scheme of things, if the extra sunlight is so negligible when it comes to producing power, why bother about the position? When the cost of panels were so expensive then yes, it was wise to place them for any extra little output they might give – and this included the angle of degrees they were set at! No-one seems to worry to much about the angle any more – just slap them down on the roof! If output is of concern to you – now that panels are so affordable – simply install an extra panel.
On my farm gate and construction site remote security camera poles, and my farm fence solar powered energisers for electric fencing, optimising efficiency from limited PV panel capacity makes a difference. For these installations i can readily orient the panel in the optimum direction.
I’ve found on my house that a mix of panel directions, some east-ish and some west-ish, has a couple of advantages
* during November to March the total generation per day is a few percent higher because the inverter doesn’t clip as much. The peaks generated by the two panel strings (~ 3 kW each) are about 3 hours apart, so the total generation is broader and flatter and less is clipped off (5 kW inverter)
* my self-consumption is about 10% higher because the generation starts earlier and ends later, which lets it cover both getting up and making breakfast, as well as preparing dinner in the early evening. (During November to March, that is)
That’s a good point, Richard. If your panel capacity is above your inverter capacity you can avoid losing the small amount of energy loss clipping can cause. This loss is in general very minor, but the gain from perfectly positioning your panels can also be very minor.
I’ve heard from an installer that it can be beneficial to have some panels facing west due to a higher FIT after 3pm. I could be wrong though!
I have 2 sets of panels with 2 inverters.
20 panels facing east. 22 panels facing west.
North side of my house could only accomodate 5 panels and south side is shaded by large trees.
This setup suits my house as “ugly” panels can’t be seen from either the front or back of the house.
It’s hard to notice they’re even there.
I also have a 12kw battery.
I don’t really care about the maximum output, as high temperatures “north facing” can reduce the efficiency of the panels altogether.
I suggest to get a battery, as most people are at work during the day which is when they are working best.
It’s much more efficient to store the suns power for use when the sun isn’t shining.
If you really care about crummy feed in tariffs, then yes, put them in the best possible position. But if energy companies will pay me only 10c p/kw then I have to buy it back of them at 30c p/kw, I thought the cost of the battery justifies getting the panels in the first place.
Get a battery and stop worrying about a 5-10% efficiency rates as the energy companies are just making money from the kilowatts you provide them.
energy companies make 20c p/kw from the energy I supply them, I cut them off altogether and kept my solar energy stored in my battery for later use.
Also, check out Sonnen Flat,
They offer a set amount of kilowatts for usage per month/year. For a flat fee.
$55 inc gst per month for 1041kw.
That’s only if you use their battery.
I’ve researched many companies services and this is by far the best value.
This is an interesting idea… BUT I can do better.
You need to orientate the panels into TWO groups, so that their production matches the peak power consumption times of the day.
Now I do not mean literally or too the minute, but if peak power consumption is from say 8am to 10am and from 3pm to 6pm, then based on the demand, then if 40% of the power needed is at in the morning and 60% of the power is needed in the afternoon – then you split your panels into these two groups with 40% and 60% with the optimum orientation, respectively.
The German example isn’t a bad one.
The largest city in Germany that is closest to the Equator is Munich at 48.13 degrees North
the largest city in Australia that is furthermost from the Equator is Hobart at 42.88 degrees South
There is a bit under 6 degrees (of separation 😉 ), seriously, Australia has more of its population closer to the Equator, where the Sun is (mostly) at its greatest intensity. So we can have a greater variation for panel alignment than Germany.
Great article, thanx Roland! 🙂
I update my old 4klw solar to 6.6klw split north & south and now my bills hve doubled what the hell,Im in nsw, my hubby & I both on age pension & only get 7cent pay back, with a bigger unit I thought would lower our bills as told by sales man
Hi Rosalie,
Thank you for your comment.
I found your solar comment a bit alarming as I am also on the old age pension and considering installing a solar system, and the more I research the more complicated my decision becomes.
I’m curious with your current savings and was it a positive result for you.
Thanks
Rick
Hi Rick,
Just because you have solar does not mean you magically have no power bill. You have to monitor your usage and make sure your usage is under the amount that you are producing. Especially if you have time of use electricity plan. I see lots of customers get a small or medium solar system and then immediately think that they can have the air con, oven, washing machine all on at the same time. You also have to make a change to your daily schedule and make sure all of your high load appliances are on during the day and have them staggered. ie wash a load in the morning, cook your lunch another washing load in afternoon if needed. Heat pump for hot water and heat during the day. Pool pump needs to fit into the equation as well.
Hi very technical article. I was reading the posts but could not find an answer to the question magnetic or true north, i think the difference is around 10-15 deg plus for mag north in Sydney which i can calculate as +12.6 degrees east
Hi Rod
The article uses true north and not magnetic north. Looking it up I see in Hobart magnetic north is 15.1 degrees (east) — the most easterly of all the capitals — but in Perth it is apparently 358.3 degrees (west).
Hi Ron,
My son and I installed identical 5 kw systems just over a year ago in Melbourne. My panels all face True North. On my sons system due to the roof design half the panels face North-East (045 degrees T) and half face North-West (315 degrees T). My sons system produces very slightly more output (0.1-0.2 Kw) each day of the year than my system. In Summer both systems maximum production is 33.2 – 33.4 kw per day. Peak production is 4.1 kw.
Paid for over 100% of my electricity useage over the past year, powering pool and solar heater pumps. Just had to pay daily connection costs. My sons system paid for 100% of useage and daily connection costs, no pool (he doesn’t need one, he uses ours :-)) Current Victorian feed-in tariff 9.9 c/kw hr.
+1 for mix of panel directions to match self-consumption at main usage times… eg NW is great to match afternoon self consumption for heating or cooling, entertainment etc.
I also believe in ~20% more panel capacity than inverter capacity. This allows fatter output throughout the day rather than a focus on peak production.
Interestingly many gum trees have pendant leaves (steep angles) to maximise solar input at start and end of days, and shut down near day’s middle when they’d waste too much water when system would be too inefficient…
Hi Ron,
We are planning to have a house built just west of Brisbane in the near future which is going to be totally off grid. The shed on which we are intending to put the solar panels can be orientated in any direction but we have been given conflicting advice in that one supplier advised us that the best orientation is to have the panels east west facing due to our power needs being more in the morning and late afternoon and others advising north would be best. Please can you provide your opinion to at least give us a bit more guidance on the way to orientate the panels as there is nothing worst than having a blank canvas to start and getting it wrong.
Cheers,
Mike,
Hi Michael
There are different approaches that can be taken so I’ll give you my thoughts without saying this is definitely the best way to go about it.
First off, because solar is cheaper than battery storage you should install a large solar system that will produce much more energy than you’ll actually use. This will reduce battery use during the day on cloudy and partially cloudy days and help charge the battery for the evening on those days. Because your solar system will produce more energy than you need on sunny days it can make sense to orientate panels north to maximize output on cloudy days when you need the energy most.
But because off-grid homes can have panel capacity that is more than 133% of their inverter capacity and still receive the STCs that lower the cost of home solar, some suggest having panels face east west is better to avoid “clipping” in the middle of the day when panels produce more power than the inverter can use, but my guess is this doesn’t outweigh the benefit of facing panels north (at around 357 degrees to be precise) to maximise output on cloudy days.
Looking at your past electricity use can give you an idea of which season you use the most electricity. Tilting panels at say 40 degrees will give a much more consistent solar output through the year than tilting at the angle of optimal annual output which is 24 degrees. Since you can’t export your surplus solar electricity for a feed-in tariff it makes sense to optimise the tilt to match your consumption.
Using the PVWatts site can let you investigate how tilt will affect average output by month:
https://pvwatts.nrel.gov/
Ronald, your advice on a big dipped northern array for grabbing lower winter sun is optimal, I figure. Yes, the East-West vs North dichotomy posed in the question isn’t all there is. There has to be considerable merit in a third option: Winter-optimal big north array being supplemented with a western array to grab afternoon sun after the northern array gives up. Powering an aircon in the late afternoon, without flogging the batteries, would have to be just as useful in Queensland as down here in Victoria.
I’m happier with hitting the batteries a bit for a microwaved breakfast and a load in the washing machine early in the day, then recharging during the remainder of the day, rather than an Eastern array powering those modest loads, then flattening the batteries for the aircon in the late afternoon, with no recharging possible before the nightime loads kick in.
Some west facing panels would certainly make sense for a household with regular high late afternoon electricity use. Mind you, my parents are nearly in the tropics and don’t use air conditioning but do heat on cloudy winter days so it will come down to individual circumstances.
Hi Ronald
I am new to the forum and trying to learn what’s best for my home
I am totally Off Grid I have 7.1 kw of solar panels and a sunny island inverter and a sunny boy 5 with 2x 13.8 BYD batteries and an 8 KVA generator set to come on at 25% battery
I am finding it quite difficult to manage the usage of power between the pool and the home
It can be difficult to have the battery’s fully charged in winter months and even if they are the split systems we have can drain them quite quickly
I am contemplating going on grid rather than spending more money on panels or extra battery and I would like some good advice .
Hi Ray
If it’s not a large expense for you to go on-grid I would definitely recommend it. Because it will let you send excess solar electricity back into the grid for a feed-in tariff it can be worthwhile both economically and environmentally.
If you do have to pay a considerable amount to get connected to the grid then you could instead consider if it would be cheaper to increase your solar capacity. This will help keep your batteries charged in winter and allow you to warm the house while the sun is up, reducing the need for heating in the evening. If possible, additional panels should be tilted to maximise winter output.
Hi Ray,
As an ex-pool owner in my previous home, I’d be reasonably sure that 7.1 KW of panels, wouldn’t generate enough to run a pool filter, and any associated chlorinator (if your pool is a salt water one), on top of a normal household consumption level, and as well, also re-charge a battery to replenish for your evening usage.
Living in QLD, you normally have to run your pool filter about 8 hours a day in summer, and 4 – 6 hours a day the rest of the year to keep it hygienic. And there may be extra as well for cleaning with creepy-crawly. A standard pool pump is usually 1 KW. So.. if your ‘normal’ household usage was (say) 15 Kwh plus (say) 7 kwh on average for the pool pump, you’d be consuming 22 kwh per day as a bare minimum for a two person household, before any extra heating or cooling costs.
Running the filter nearer dawn and twilight is more effective for chlorination purposes, as it gives the chlorine more time to be spread through-out the whole pool and kill off the ‘nasties’ before the chlorine level in water gets rapidly lowered by direct sunlight, Having some pool shading helps too.
Throw in some extra heating in winter, or air-conditioning in summer and I can see why you would be struggling to fully replenish the battery. Ron’s suggestion of extra panels tilted to maximize generation later in the day ( and maybe perhaps facing somewhat westerly) would seem to be the best alternative if you want to remain ‘grid independent’.
I wouldn’t count on the FIT being around forever either.
I’m not sure either what you meant by ‘off-grid’ – ie. restricted to just being off-grid for only electricity, or being fully self-sufficient. With rainfall decline/drought here already with more to come, water supply for a pool could be difficult or very expensive to source in the future. Evaporation rate will almost certainly rise.
The old adage : ‘A swimming pool is a hole in the ground that you pour money into’ may well take on an added meaning in the near future.
Re pools: I run a pool on timed day running. I use an Eco-pump (inverter driven) that use MUCH less power. I would also suggest using a silver Ioniser. Normally these are used with non-chlorine oxidisers, but I suggest using chlorine, as a chlorinator in a salt pool or other form of chlorine. Personally, I use a passive liquid chlorine feeder (a copy of an Aquinqator: a yankee patent). You can reduce the chlorine: personally, with my sysytem I run 1 to 1.5ppm, about half the normal. I also do not use stabiliser (Cyanuric acid) which is a poison. (The chlorine gets replenished when the pump runs).
If you are contemplating going off grid, I would recommend HEAPS of panels: 15-25 Kw if you want to be reliably off grid. You would also need 3 days storage & a backup generator. Not a cheap option!.
Personally, I think Grid connection is still viable unless the connection cost get unrealistic. I feel the daily cost is low compared to maintaing a rel;iable off-grid system.
Hello
I am a real novice in regard to solar just beginning to try to navigate through
I had been recommended to sunboost by a neighbour
A friend then told me about another company called sun solar
I have tried to research but wind up so very confused
Can you spare the time to assist me please
Thankyou
Sue
Holland
Hello Sue
Here is our Sunboost review page. I strongly recommend clicking on “See Australia-Wide Rankings” to see how they compare to other installers:
https://www.solarquotes.com.au/installer-review/sunboost/
Sunboost is the trading name of Bell Solar and the NSW Commissioner for Fair Trading decided not to renew Bell Solar’s electrical contractor licence:
https://onestepoffthegrid.com.au/one-of-australias-largest-solar-installers-fights-to-retain-operating-licence/
I am not familiar with Sun Solar.
If you want to receive quotes from installers we have vetted and know only do high quality work, you can get them through our website here:
https://www.solarquotes.com.au/quote/start/
Just enter your postcode and then answer the questions that come up as best you can.
Hi Ron,
Thanks for your comments which are more than valuable as we are novices when it comes to solar power. In considering your comments and those made by Erik above it would seem that a north facing array with some west facing panels would be the way to go. Would you be able to advise on how many west facing panels would be recommended. The system we are considering consists of 10Kw array with 25Kwh of batteries.
Cheers,
Mike.
That will depend on what you expect your afternoon electricity consumption to be like. If you think you’ll be running one room air conditioner you’ll need less late afternoon solar power than if you are planning to run a large ducted air conditioner that cools many rooms.
Six kilowatts of north facing solar with 4 kilowatts of north-west facing solar may meet your needs while only resulting in a small reduction in total output compared to having 10 kilowatts facing north. But without knowing more details that’s only an educated guess. Whoever you chose to do the installation should be able to plan your solar arrays so they’ll be appropriate for your consumption patterns.
Ronald & Mike,
agreed, but it does depend on the roof. Be careful if there is ANY overshadowing. In my 2 private installations, I have on the first:
10Kw Fronius with 13Kw of panels, 10Kw on the west, 3Kw on the East. This is on a roof with virtually no possibility of shading. The future possible potential of shading from some trees on the west was allowed for by setting all potential shaded panels in one string to minimise any possible losses. There are no optimisers required on this system. This system averages better than 40Kw/day.
The second system:
2 Phase, so 2 Solar Edge 5 Kw inverters, with 14.5Kw of panels with optimisers. This is set up with 14 + 14 panels on the shed roof on abt 20 deg tilts facing North (14 on each inverter), then 12 + 12 panels facing west on 15 deg slope. This has tree overshadowing after abt 14:00. The Optimisers do a great job on this system, & it averages so far also around 40Kw/day. The advantage of optimisers is the strings can be unequal on the inverter, & the optimisers compensate for the low performing panels so everything just works. (Micro-inverters are another option too). This system has some recycled panels because it is over the 33 percent allowed for rebates: This system replaced a smaller one damaged by hail. The best o/p over summer was 86Kw, & regularly over 75Kw. I am in Lismore, NSW. (Only installed in November, so no longer term data).
So, my recommendation is to see how many panels will fit, any overshadowing issues then design the system around that. Use the 33% extra panels on the inverter if possible to fit. Use either optimisers or microinverters if there is any shading, or if the string is split on 2 directions.
The (cricket ball sized) Hail damage was interesting: the earliest 180W panels were OK, but the newer 275W panels initially inspected after the storm were OK, but after 6 months of heat-cold cycling I inspected them & of the 15 panels, most had micro-cracks in some cells. The glass was not damaged. This was evident as cracks radiating from an impact point on damaged cells: possibly a single cell damaged on one panel, & multiple cell damage on other panels. The insurance company replaced the system after I had quoted both repair & system replacement (then added my money to really increase system size!). So, if you suffer hail damage, have the panels checked 6 months or so after the initial storm too!
Thanks for the article. A little bit (alot) of it was over my head so hoping I could get some advice.
I’m in the process of getting solar and because I have limited roof space, the largest north-facing system I have been quoted is 4kw (13x315w panels), which would put a dent in my electricity bills but not as much as i’d ideally like.
I asked the question about using the south facing side of my roof and they came back with a new quote adding 8 of the same panels for an additional $900, and going from a 4kw system to a 6.6kw.
We average about 20kWh usage per day and night usage varies from very little to either a split or a couple of column heaters during the really hot/cold nights.
So my question is, does the additional $900 warrant the benefits i’ll gain from adding the south facing panels? I’m not sure if it shortens the payback time but the place that has quoted me said it would by potentially a year.
Hoping to get a second opinion please and my apologies if any of the terminology i have used is incorrect.
Hi Michael
I’d say it’s almost certainly worth it because you are getting an extra 2.52 kilowatts for only $900. I don’t know your location, but south facing panels will typically generate at least 70% as much as those facing north. Even if you are in Melbourne you can expect those eight additional panels to produce around 2,250 kilowatt-hours a year. In Melbourne it is possible to get an 18 cent solar feed-in tariff, so even if you never used any of that solar electricity yourself it would lower your electricity bills by $400 a year and so pay for itself very quickly.
I’d say the only reasons it wouldn’t be worth it is if the southern roof suffers from shading or possibly if you can’t get a good feed-in tariff for some reason.
Thank you very much Ronald. When you put it like that, it seems like a no-brainer but makes me wonder why they didn’t mention using the south facing side in the initial consult. Either way, i’m happy i asked the question and will be definitely going down that path.
Thanks again.
So, by nature any southern facing roof line will technically be”shaded” due no direct sun…
I know they will generate some electricity, but when you refer to shading what do you mean?
In Australia south facing roofs get direct sun. Unless a roof is exceptionally steep it will need to be a lot closer to the south pole to never get sunlight on it. But the sunlight energy will be less per square meter of roof reducing the output but a little under 30% compared to north facing panels in most of Australia. By shading I mean shade from trees or whatever blocking sunlight falling on the south facing roof.
Hi All, can someone please tell me how much efficiency will be lost if solar PV panels are installed facing South at 8 degrees. I am not sure how to work that out. I have a friend building a house that wants his roof facing south, and wants to install 8kW of PV, but I fear he will be throwing away money,. I am trying to suggest that he should instead try and have enough north (or NE/NW) facing roof space for his PV system. Personally I find facing solar panels south crazy, but I need some numbers to put him off the idea. Any assistance would be greatly appreciated, by me and the environment : ) Our postcode is 4220 (Gold Coast). Latitude of 28 degrees. (so I think ideally, solar north at a 28 degree pitch would maximise the efficiency?)
Hi Ben
If his roof only has an 8 degree slope then panels facing directly south will produce 90% as many kilowatt-hours annually as ones facing directly north on that slope. You can check this using the PV watts site:
https://pvwatts.nrel.gov/
The closest available location it provides information for is Brisbane, but it should still be reasonably accurate.
So while it would be better to have north facing panels, south facing ones aren’t a huge problem at the Gold Coast’s latitude, especially with a gently sloping roof. But your friend should be aware his winter solar production will be low compared to summer.
We average 9 kwh per day. Only two of us living in the house. Is it worthwhile installing a 6.6kw system.
Hi Ian
For most households a 6.6 kilowatt solar system is worthwhile. I don’t know where you are but a solar system of that sized that doesn’t have any significant shading is likely to produce 8,500 kilowatt-hours a year or more. Even if you use none of that electricity yourself and send it all into the grid for a 12 cent solar feed-in tariff it would still lower your electricity bills by around $1,000 a year. As you actually will use some of that solar electricity yourself, the results will be even better. If you spend $5,000 getting a good quality system from a reliable installer it would pay itself off in under 5 years. Generally it’s only people whose roofs suffer from bad shading or have special circumstances who won’t benefit from solar.
Thank you, we are in QLD Fraser coast.
We are will be getting 20c FIT from AGL.
In that case it should be a very good idea to get a 6.6 kilowatt system. It’s likely to produce around 10,000 kilowatt-hours a year. If that is all sent into the grid for a 20 cent feed-in tariff that’s $2,000 off your electricity bills each year. As you’ll use a portion of the solar electricity yourself the savings will be even greater.
Hi Everyone,
We have had solar panels for a while now and I was recently told by a friend that all the power they generate goes straight to the grid and you buy back what you use. Therefore this friend was saying to use power in cheaper off peak times such as during the night for pool pumps and dishwashers etc.
I have always run all my big power using items at seperate times during daylight to try to use the power we generate with the solar.
Can anyone clarify if the power goes straight to the grid or whatever isnt used in the home goes to the grid?
Thanks, Shell 🙂
Hi Shell
In most cases your friend wouldn’t be correct, but it is possible.
Firstly, if you are in NSW they used to have gross metering which works as your friend describes. If you live in NSW and got your solar before the end of 2016 it’s possible you still have this. In this case you are almost certainly be better off if you change to net metering, which is what is now normal throughout Australia. Electricity retailers are now responsible for electricity meters so you will need to contact them if you want a change.
Another situation in which your friend could be right in that you will save money on your electricity bills by limiting your electricity use during the day is if you have an old high feed-in tariff which pays you more for the solar electricity you send into the grid than you pay for grid electricity. In this case limiting electricity use during the day can save you money by increase the amount of high solar feed-in tariff you receive. (Although the people who operate the grid don’t like it, as they’d prefer you to use more electricity when the sun is shining.)
Hi Ron
Great article. Thanks
My dilemma is that the house I’ve just moved to has a problematical roof line – 2 stories with lots of different directions and I have been told by 2 companies that I can only get 1kw on it. They both got quite annoyed when I questioned the viability of having 1kw. In my previous home I’d put 1.5kw in and it was no where near enough.
I don’t think that the roof is that small
And no one has mentioned micro inverters. Would that be a viable option?
How can I find a trust worthy company to get info/help and believe what they tell me
Cheers
Hi Linda
What is possible will depend on your roof and your wind zone — requirements are stricter in cyclone areas — but unless you live in a toadstool pretty much every roof can have more than 1 kilowatt installed on it. A common solution for roofs like yours is to use microinverters. These are small solar inverters that go on each panel. These make them independent from the others so they can face any direction. Other options are to use a string inverter, which is what most solar homes have, but use optimizers on the panels so they can face different directions. Another option is to use Maxim optimised panels where the optimization is built into the panels and this can be a low cost option. The unfortunate news is, no matter what method is used, it will be more expensive than if your roof had large flat areas that are easy to install on.
I would guess the two companies you contacted are not interested in difficult jobs and are only interested in jobs they can do quickly and easily. If you want some to get some quotes through us from installers we know do good work, you can go to our homepage:
https://www.solarquotes.com.au/
Then enter your postcode in the space at the top right and answer the questions that come up as best as you can. You can mention you have a roof that is difficult to work on so they will know in advance what they will need to deal with.
We have a new 20 panel 6.6kw with 5kw inverter
But the inverter only records a max of about 4.6kw
Why should we have got a bigger inverter?
Or is there a loss due to inversion?
Then it appears that despite the inverter reading
about 4.5kw for four hours on a good day
the meter output to Energex only records about 4kw
Do we lose power through each change?
We are on the Gold Coast
Hi Bill
It is likely there is nothing wrong with your solar system. This article goes into a number of reasons why a system with a 5 kilowatt inverter will usually produce less than 5 kilowatts:
https://www.solarquotes.com.au/blog/5-reasons-your-solar-system-power-is-lower-than-you-expected/
If you are concerned you can keep track of the total output produced by your system and see if, over time, that matches what is expected from your system. (If you want help with that you can leave another comment and I’ll give you a hand.)
With regard to your second question, if your solar system is producing 4.5 kilowatts and your electricity meter says you are exporting 4 kilowatts that will be because your home is consuming 0.5 kilowatts of solar energy. The power produced by your solar system will be used by your home first and then any excess will be sent into the grid for a feed-in tariff.
Hi Ron
BREAKFAST TIME
These charts showing panels facing various angles generating lots of electricity are fine however I am concerned that my NW facing main roof won’t start generating much electricity until after I have eaten my breakfast.
When I eat breakfast I like to use high energy consuming devices like a kettle, toaster and microwave. Do you have any charts that can estimate how much electricity my panels will generate at what times in winter and summer. I have very limited space on my SE facing roof and I doubt many installers will want to squeeze in extra panels by overhanging roof edges and gullies and tilting sideways. I have lots of space on my SW facing roof but doubt there are any common inverters that can handle 3 directions.
If I get a 6 ½ KW system it would be nice if I could be getting close to 2,000 watts at breakfast time for most of the year cloudy weather excepted.
My guess is that the economics of solar for me will be substantially reduced if I cannot get the panels to produce enough power to cover my energy intensive appliances at breakfast time.
Have you seen slightly less powerful kettles and toasters that don’t draw too much power at meal times ?
Regards
Michael
I’m afraid we don’t have any simple charts as it depends on the pitch of your roof, your location, and time of year, so it gets quite complicated.
I can tell you that in the middle of winter in Sydney, if your roof has a pitch of 22.5 degrees and faces directly east, then one hour and 15 minutes after sunrise solar panels on it would be producing a little under half the power they would at noon. But this information isn’t very useful in practice and is complicated by the fact that any panels facing other directions would also be producing some power.
But I don’t think you need to worry too much because, while kettles, toasters, and large microwaves may use a lot of power, they don’t use a lot of energy. This is because they are only used for a few minutes each morning. So if a 1,000 watt toaster is used for 3 minutes it will only consume 0.05 kilowatt-hours. So they are only likely to make up a tiny portion of your total electricity use.
But if you want to maximise your early morning solar production anyway, you have a few options. Under the right circumstances, a flexible inverter such as a Fronius can handle panels facing three different directions. It’s also possible to use solar panel optimisers or Maxim optimised panels to face panels in 3 or more directions. Microinverters allow each panel to be completely independent from the others so each panel can face a different direction if desired.
But note, if you have a large section of roof that faces roughly north, the best solution may be to simply put a lot of panels on it, as each panel will still generate some power early in the morning.
Michael,
I have not read all the recent comments, so pls forgive if I am repeating something already said.
Generally, if you have enough suitable roof, my preference is soime panels facing easterly, some facing westerly direction. The idea is to overpower the inverter. Then the East facing panels generate something early, in the middle of the day all panels generate something, then in the afternoon (which is generally the most ´useful´ time) you get power into the late afternoon. The idea is to widen the peak generation time to a flatter curve.
On my system, that suffers from overshadowing at various times, I have a Solar Edge system with optimisers. When we installed this system, it was 2 of 5Kw inverters, with the maximum rebatable panels (46x300W). I have plenty of roof space, & the system is on a shed, so I have added used panels to bring the system to currently about 15Kw of panels. It starts generating early, then gives output until dark, with a best of 80KwH generated one day last summer.
I am not a Solar PV professional, but a well trained enthusiast. My advice would be to put as many panels on the space available as possible as long as there is direct light some time during the day. If there are any shadows on any panels, either use micro-inverters, or optimisers.
With optimisers there are some constraints in design (mainly in Solar-Edge case making sure there are sufficient panels in the string to generate voltage early & late in the day: in my case I have strings of at least 14 panels.) The panels can be mixed type & orientation with optimisers. In fact, optimisers are a good way to upgrade an old system. Leave the old panels on the roof, but fit optimisers. Fill the area around with new panels with optimisers, & a new inverter. This saves the re-cycling costs of scrapping the old panels. Any panels down on output can be seen on the optimiser display then replaced by a similar sized panel if an old one.
regards, Doug
Dear Ron
Many thanks for your answer. That is very helpful. Where I live in Western Australia the buyback rate is only 7 cents a KW so unless you are using solar power for high energy consumption during the day like an airconditioner or batteries the daytime solar energy production is of very little value to most people. To get the maximum value out of the system matching energy production with breakfast and dinner time energy use is probably the most useful thing you can do from a financial self interested point of view.
If someone could come up with a computer model to analyse this it would be fantastic. Maybe something less complicated could be created using EXCEL that required a bit of manual fiddling by the user.
My question is not simple. I live in the metro area of northern Perth. I have an east facing house. The north side of my house has a airconditioning system on the roof. I have a large 60 foot tuart tree in the back yard and have no intention of ever removing it. It shades the west side and north of the house completely in the afternoon. There is another 25 foot tree in the front side garden which once again stops the sun on the north side of the house for part of the mornings. My husband does not like the idea or the sight of panels on the east side (front) of the house. The south side of the house SEEMS it may have sun all day but the panels would need to be raised up to face the north. I would love some advice as to whether this would be practical. My husband asked a company some time ago and they came back saying that it was impractical for us to have solar panels but were not asked about the south roof north facing panels. I would like to know if it is at all possible. Thanking you in anticipation.
Solar panels installed on a south facing roof in Perth will produce 74% as much energy as north facing ones. This means south facing panels in Perth will produce nearly as much energy over a year as north facing ones in Hobart. Because solar has fallen so far in price this can be worthwhile, although it will increase the payback time. This is without raising the panels up on tilt racks. Because of their extra expense, I generally don’t recommend tilt racks. Also, Councils may not allow them.
I generally recommend getting a system as close to 6.6 kilowatts as possible in Perth. The best arrangement may be to have one set of panels on the south facing roof and another on the north or west facing roof, depending on which is best from the point of view of shade and space for panels. Of course, you could decide on a smaller system just on the south facing roof.
It will depend on how much you pay, your electricity consumption, and what the shade conditions are like, but south facing solar may have a simple payback time of 7 years.
Your situation in not being able to fit panels is not unique.
There may be options tho: here on the Eastern Seabord, we have a community owned power reseller called Enova. They have a project where you can buy panels on a ´Solar Garden¨ that offset your account with Enova. I am suggesting there could be a similar project on the West coast (Check with one of the sustainable energy groups who may know.)
How Solar gardens work is that panels are installed on a commercial premise that can use the power. They have a long term supply contract so the investor gets a return which is offset on their electricity account. Win-Win for everyone.
If you do have another look at your house, consider all the other areas that might hold panels: over a shed or carport for instance. South facing panels can work, but so can panels in shade: you just need more panels to get reasonable output. These panels should be connected to micro-inverters, or optimisers, so low output panels do not affect the overall performance. There could be other options developed in time too: such as Solar tiles.
Hi, We bought a house recently which already has a 5kw/22 panel system on it west facing as our house is a Unit and we only have use of one side of the roof area and as we live in a remote area of Qld we can only go with Ergon and they only pay 7c pkwh feedback. We have found our bills to be quite high still so ordered another 5kw system from Sunboost with 16 X 370w panels for $3891, however when installers came to put the system on they said they could only fit 7 panels on the north facing small roof and would have to get the company to requote as they were not allowed to install on south facing roofs…Quote came back for a 3kw inverter with 7 x 410kw panels for $2451 stating that As per the CEC guidelines, they cannot install any panels in South direction. We are totally confused and not sure how to proceed now, we really wanted another 5kw system, are you able to offer any advice please ?
Hi Claire
Before agreeing to go ahead I suggest reading online reviews for Sunboost. Here is our review page for them:
https://www.solarquotes.com.au/installer-review/sunboost/
Be sure to click on “Aus Ranking” so you can see how they compare to other installers in Australia.
Installers are permitted to install south facing panels if homeowners want them. They were either unaware of this or don’t want to install on your south facing roof and claiming they can’t as an excuse. South facing panels will produce around one quarter less energy than north facing ones on a roof with typical pitch.
One option is to go with another installer and perhaps get 14 panels if that’s all that will fit — 7 facing north and 7 facing south.
Another option is to have your old solar system removed and replaced with a larger solar system. If you get 22 panels of 370 watts that would come to 8.14 kilowatts. While this is wasteful in the sense that you’d be getting rid of a functioning solar system, because larger solar systems generally cost less per watt and because of the advantage of having everything covered by a brand new set of warranties, you may want to consider it.
Finally, you can not do anything and could try to conserve electricity in other ways and possibly replace your existing solar system with a larger one when and if it develops problems.
Note that if you get a larger solar system installed and you have single phase power it will have to be export limited to 5 kilowatts. Despite this, getting a larger system such as the 8.14 kilowatt system I mentioned above, can still make sense, especially if your electricity consumption is high.
I agree totally with Ronald. Personally, in your situation, I would look for the areas that draw the most current: It might be an older air conditioner (units built in the last 5 years are much more efficient). Also check how the hot water is heated: it might be that the system is a storage tank on 24/7. For a 315L tank, without off-peak power, you can fit a time switch to turn the power on to the HWS at say 10am, then off at 2pm. This will use solar when the sun shines (& the few days there is no sun, the costs are bearable). If the unit is not on town water, does it have a pressure pump? They are notoriously power hungry (& can be replaced by an efficient ePump now). Is there a septic treatment tank? The older tanks can have inefficient air pumps (The Taylorex tanks can be upgraded for less than $1000 & pay for the upgrade in about 2 years for instance.)
You can look at the specification plates on appliances to get an idea of current use. Also, you can buy a plugged power meter to check plugged appliances.
Also check for Halogen lights, & change them for cheaper LED lights.
Good luck! Doug
Great feedback thanks very much we will hold on upgrading atm then look at 7.6 system in the future replacing what we have which is only 2 years old meantime monitoring our usage thanks again
Shade on the roof in the bush can be a problem Effectively moving sunrise by a few hours. Would be good to see optimisation take this into account.
How about a roof redesign to provide for a walkway to be able to clean the panels. ie redesign the house from scratch, with a single skillion roof and a sun platform above to do the cleaning. Especially in bushfire areas to remove leaves.
If shade on the roof is a problem in the bush, then the best optimisation I can think of is to cut down or lop the offending trees. (Mine are 55m away, so they’ll have to grow more than available rainfall will ever allow, if they’re to intrude.)
When I designed the new off-grid build (just about complete now, if that plumber will just take a break from his 5 other houses, and get back to finish off), rather than provide for going up onto the roof for cleaning, that’s been designed in. The 25m long northern skillion is at 40 degrees primarily to catch the winter sun, but that should also cause all leaves to fall out, and help rain rinse the panels well.
The steel decking profile has a matching available array racking clamp, rated to 40 degrees roof slope, so there will be no roof penetrations when the array is finally installed.
It’ll fit 22 panels, plus 9 on the western hip – for grabbing the setting sun on a 43 degree day, to power the aircon as long as possible. (It’s not going to compete with my brother’s new 20 kW + 10 kWh battery install, though. He’s exported 377 kWh in the last week, as self consumption is only 20 kWh per day. Why? He had the roof area, and 20 kWp is probably only 6 or 7 kW in winter at best.
The trees are a problem when on the neighbours block or on the road.
Are the rails for the panels on your system horizontal on the roof, or aligned on the “vertical” sloping profile?
With the local Mens Shed we went off grid with a 24 V !0Kw LiFePO4 battery system maximising the efficiency by using 24V lighting – saves converting back to 240VAC and the 10% efficiency loss.
Still had to put in an inverter for the Fridges. Trying to igure out hw to use the excess power when everything is charged. Best candidate is a Low Voltage ZIP water heater to make coffee!!
Can you update the article with graphs of performance for all orientations (south facing too)?
THe best direction is the direction of THE SUN WHEN YOU NEED THE MOST POWER
Hi Ron,
Thanks for your valuable information. Very interesting reading! I currently (no pun intended) have a 2 kw system that is 7 years old and functioning well with quality components, facing north. I would like to increase the amount of solar on my roof and there is space. Should I just buy another seperate system and have 2 running, add more panels and upgrade the inverter or scrap the old system and buy a whole new larger system?
Generally I recommend removing your old system and putting one large new one in so you’ll have all new equipment covered by a brand new set of warranties. This is because while your old system could run for another decade or more without a problem, it could fail in six months and you’d be out of pocket to have it fixed. Because new solar systems are usually cost less per kilowatt the larger they are it can definitely be cost effective. Another consideration is the old system may take up a fair bit of roof space as the panels may be 200 watts or less.
Of course, if you are confident your old system will function well long term, you can keep it and put a second system in.
Thanks Ron, new 6.6kw system it is. I will use your website to get some quotes. I have heard there are some systems that will give you limited supply in times of power out. Worth the extra? Also, I plan to add battery in a couple of years when prices come down. Are all systems sold now ready for battery addition? Thanks again for your advice.
Unless you are in a particularly blackout prone area I wouldn’t worry about paying extra for an inverter than can supply some power during a blackout. It is possible to install batteries that work with any solar system. The Tesla Powerwall 2 is an example of one of these. If you are planning on getting a battery in the future I would recommend considering getting a larger solar system. This will help keep your battery charged during winter when solar output is low and electricity demand can be high. The extra solar generation will also be useful if you decide to get an electric car.
Ok that’s interesting. My next car will be electric, probably within the next couple of years. I think the battery technology is improving rapidly and am just marking time till prices come down. I’m actually hoping to get a car that will act as my feed in battery as well if it can all come together. So what size system would you recommend?
Basically, within the limits of your budget, I recommend installing as much solar as will reasonably fit on your roof. Depending on where you are, you may need to install an export limited system if you have single phase power, but this can definitely be worthwhile. While it is possible some generation will be lost, this can usually be avoided by having devices switch on in the middle of the day. Once you get a battery that will also help prevent surplus solar energy going to waste.
This page gives the connection rules by location:
https://www.solarquotes.com.au/grid-connection/
If you can install 10 kilowatts of panels you can be pretty confident you’ve future proofed your home.
Ronald,
I think this needs a little clarification, to help people make a wise choice.
1: Adding to an old system is difficult because the standards have changed over time. Old panels may not have the same fire safety as new systems & earthing requirements have changed.
2: Racking changes: some racking systems are nla, so it is not possible to add easily to these systems.
3: Difficult to mix n match panels: different specs, sizes, outputs.
4: If space restricted, new panels are usually more efficient.
However, for those lucky enough to have a big shed, old panels can often be ´recycled´ onto a shed (or non-domestic building. If Optimisers or micro-inverters are used, panels can be mismatched: subject to design constraints)
In my case, I re-used some old panels in my system that is fitted to a farm shed. I am adding to that with a Victron Mppt to charge (& help restart) my battery backed system if the power goes down for an extended period (ie days). It is possible to way over-power an inverter, as long as Solar credits are not claimed on the excess. Particularly useful for E facing & W facing orientations (where the maximum power is reduced: the idea is to flatten the power generation curve). Again, seek advice on what is possible.
The other thing to keep in mind is that big inverters are now not too expensive. Even if Grid export is restricted to 3Kw (as many rural NSW customers) or even Nil export, as long as one can use or save the power it is worth considering. EVs are one area this can be used (but also.pools, hot water, Washing machines, A/C, etc switched on during the day)
Heating water is one obvious use of excess solar. Hot water can also be used for building heating.
Hi Ron,
I am currently considering two options for a new system located in Brisbane:
1) 6.6kW system
– 11 panels facing 74 deg from North
– 7 panels facing 344 deg from North
2) 9.7kW system
– 11 panels facing 74 deg from North
– 7 panels facing 344 deg from North
– 7 panels facing 166 deg from North
I have two questions really. Firstly is is worthwhile to maximise production with option 2? I assume your answer is always yes.
Secondly, do you see any issue with connecting the north and south facing strings in parallel to one MPPT on a Fronius 8.2kW string inverter? I have read about the benefits of connecting east/west-facing strings to a single MPPT but can’t find anything about doing the same with north/south strings.
I considered micro-inverters for this layout but my modelling doesn’t justify the additional cost.
Thanks,
Tanja
Hello Tanja
A panel facing 166 degrees from north will produce 85% as much energy as one facing 74 degrees from north and 78% as much as one facing 344 degrees from north. They will increase the total energy output of your system by around 32%. If the 9.7 kilowatt system costs less than 32% more than the 6.6 kilowatt system I’d say it’s worthwhile. Even if you have to pay a little more you may think it’s worth it to be prepared if you get a battery or electric car in the future.
System design is complex and exactly what can be done depends on the model of panels and location, but if you are using a reliable installer who does quality work it will be configured correctly. If we referred the installer to you we will guarantee their work with our good installer guarantee, so you can be very confident you’ll get a well designed system.
The real question is ” What power do I need and when?” Then choose the direction that suits best.
Hi Ron,
Thank you for the article.
We have 2 properties, both are inland, one is between Sydney and Canberra, the other is between Canberra and Melbourne.
I would appreciate any advice to work out optimum orientation for PV for these properties.
I’m wondering specifically:
1. Would your optimum orientation for Sydney depend on whether you are located in coastal Sydney vs western Sydney (assuming other variables like topography and what not are equivalent)?
2. What factors cause your optimum orientation for Canberra to be 16 degrees west of that for Sydney? One of our farms is in hilly country near Marulan NSW (latitude -34.7)… half way between Sydney – Canberra.
3. What factors cause your optimum orientation for Canberra to be 12 degrees west of that for Melbourne? One of our farms is on open flat land 30km west of Wodonga Vic (latitude -36.1)… on the Hume Hwy about half way between Canberra – Melbourne.
We have multiple small PV installations for electric fencing, irrigation/bore pumps and so on. But we are just now looking at remote PV/battery powered cellular security cameras on poles at gate entrances. Optimising orientation will make a difference for all these installations.
I am a novice who has received contradictory advice from local solar installers.
Thank you, Gus
Thank you for the valuable information. after reading this article I was empowered with fact and myth about south facing roof.
Hi, what about Alice Springs? And for tilt as well? We get very hot in the afternoon… Though that is also when we want to use air conditioning! Thanks.
According to the PVVWatts site:
https://pvwatts.nrel.gov/
In Alice Springs, placing panels 5 degrees east of north results in a very small increase in output compared to facing them directly north. The best tilt for overall annual generation is 26 degrees. (Probably closer to 26.5 degrees if you want to be really picky.)
Of course, if you want to generate more electricity in the afternoon for air conditioning you may get more benefit in practice from west facing panels. Also, you can increase tilt to improve winter output or decrease it to improve summer output.
Hi,
Im putting a 6.6kw system on my roof. The panels will face both East and West. Im an hour southwest of Brisbane.
Im getting 15 x 440kw Panels.
Whats the best way to divide them up between the East and the West roof.
That is how many on each side for the best overall daily output?
Also my roof is very steep. Atleast 40 % could be more 45%
And if they are divided between the East and West does that mean that while the sun is on one side..the panels on the other side will not be producing much energy?
Thanks, Appreciate any feedback.
With the steep roof you will get Excellent early morning sun and late afternoon power. I have 10 kw 5kw east and 5 kw west, but only 22 degree pitch. Separate inverters with a limit set to 5kw to the grid. Problem is too much power at midday, so always throttling to limit power at this time. You won’t have this issue. 16 panels 8 + 8 would be better.
Thats a steep roof! I would try to put extra panels on if possible. I would think when the panels slope that much you may find a dip when the sun is overhead.
I installed an E-W system, & put abt 1/3 facing East because the time power is needed most is later in the afternoon.
If you can fit more panels & have the money available, I suggest fitting a bigger inverter & more panels. Also remember if you have been quoted with String inverters, any shade can reduce the output. Also are you in a potential flood area? If so consider Micro-inverters or Optimisers. A SolarEdge system reduces the string voltage to a safe 30V if the inverter is off. This is really important in an area subject to Flooding where people might be trapped on a roof. (Microinverters are also safe I feel)
regards Doug (based in Lismore, & an Enova Energy Coach)
Hi Gail
For a household with typical electricity consumption, you will be better off putting more panels on the west side than the east. This is because in Brisbane people tend to use a lot more electricity for late afternoon air conditioning than morning winter heating. So you may want around two-thirds of your panels facing west and one-third facing east. Note the number of panels on the east side can’t go too low, with the minimum number required depending on the inverter used.
Because of your steep roof, panels on the east side will produce a lot of energy in the morning. If they are at 45 degrees then the panels one the east side will produce the most at around mid-morning while the panels on west side will produce the most around mid afternoon. The east facing panels will produce very little power a couple of hours after noon, while the the west facing panels will produce very little power a couple of hours before noon. The good news is, the overall amount of energy your system will produce will only be a couple of percent less than if the panels were at a more typical angle of 22.5 degrees.
If you are interested in getting a larger solar system, in the Energex area which Brisbane is part of, you can request permission to install a solar inverter that is larger than 5 kilowatts. It will have to be export limited to 5 kilowatts, but on your steep roof this won’t be a problem. (Not unless you get a very large solar system of over 10 kilowatts.) If your household electricity consumption is high, then I’d definitely suggest looking into this and it will also prepare your home for if and when you get an electric car.
… to add to Ronalds comment, if it is possible to mount the inverter near where you park your car, you could consider an inverter with a built in car charger. Not a lot more now, but saves a big cost later when you finally buy an EV.
Some hints: try not to install your inverter on a Western wall: the harsh afternoon sun shortens the life of inverters. South side is best, but E OK too.
regards, Doug
Hi
Ron and Doug thanks for your feedback.
On the west side i have an issue with tree shading covering the lower half of the roof around 2.30/3pm onwards in winter. I can fit 6 or 7 panels across the upper west roof,..but more panels below them would hit the tree shade when sun gets lower in sky. Mostly no shading occurs on the East side of roof..except from a small tv antenna. ( I have 15 panels in total to find good placement for)
I wouldn’t like to cut the medium height trees, as they offer great protection from sun and wind in my immediate backyard. But i have read tree shading reduces output alot and microinverter an expense id like to avoid…but if they are on only a few panels..might be worth it.
I have considered putting the panels on my large flat roof shed..but it gets alot of shading from a large gum on my northside and the neighbours tall tree too, mostly in winter. Think less shading would occur in summer when sun is higher in the sky. But the roof also slants 5-7 ° Southward. Its been hard to work around these issues. I would prefer to have them on the shed.. and inverter in shed, next to shed electric subboard.
Any further thoughts would be appreciated.
Gail,
I would consider a SolarEdge system: slightly more expensive than a string inverter system, but the panels then are optimised for maximum output. (My system at home is SolarEdge). I have 15Kw of panels & 2 of 5Kw SolarEdge inverters. Even on overcast days I get 12>20Kw generated. I also have afternoon shade. My panels here face N & West, with a few to be added facing East. You did not say if you are in Qld or N NSW?
As far as the Shed goes, it is possible to fit the panels on tilts, & Back to back facing E & W approximately. (so the panels tilt at least 15 degrees to aid the rain cleaning the panels, with one row facing E, then immediately behind a row facing W, then a gap, & repeat.
One thing to consider is that on the Shed, it is possible to use S/H panels. With the SolarEdge system, one can mis-match panels too (even mixing lower wattage panels with higher). fyi, in my system I am using a few hail damaged panels. With the SolarEdge I can monitor panels individually so if the output drops, I will change the panel. Used 250W panels sell for as little as $30. Installation & rails add to that cost tho. Personally, I would think about a future EV when installing the inverter (with built in EV charger).
To give an idea about running a (Hyundai Kona) EV: I have gone nearly 60000Kms in 2 years. Initial cost high, but low servicing costs ($165+$250+$165), virtually free charging off the PV system & even commercially charging the most I have paid is abt $10/100Kms. Compare that to current petrol costs!
Hi again, Gail.
If the lower roof is shaded from 2:30 onward, then any panels there will have their output severely cut, no matter what steps are taken. Unless you are willing to trim the trees, your best bet may be to put as many panels as possible on the upper west roof and the rest on the east roof. While the east-facing panels on your steep roof will produce little power after mid-afternoon, they will still provide some and that will help meet afternoon loads. If you get a system of 6.6 kilowatts or close to it, then you will have a roughly equal split between east and west panels. If you decide to get a system over 6.6 kilowatts then you’ll have more east-facing panels. This is not necessarily a problem, because you can set your hot water system to switch on in the morning to take advantage of the solar energy produced. You can also make a point of shifting other electricity consumption to that time if possible.
Great article and love all the comments too! I hope it’s still active..
I’m looking at getting rooftop solar for my roof in Melbourne. It’s a flat roof so I assume I could face the panels any direction? We have electric heating, cooling, cooking and an EV and I’ve analysed our load over the last year. Winter has by far the greatest peaks, around 8am and then evenings. There is also a bit of a peak in summer evenings.
I’m wondering both which direction to face the panels and how big a system to get.
It will be hard to shift the 8am winter morning peak but I think we could bring the evening heating forward to the mid afternoon when there is still some sun (hopefully – Melbourne winter!).
For the direction, I was thinking of 1/4 facing NE (and maybe a steeper angle) to get some morning sun in winter. Another 1/4 facing N to just give us something through the day. And the other 1/2 facing W for summer afternoon pre-cooling as well as heating in winter before the sun goes down. And also just because exports at that time (e.g. in summer) are more valuable to the grid than the middle of the day.
In terms of the system size, we average over 30 kWh/day in winter. The heat pump draws around 6 kW when heating and I’d like to be able to cover that for “free” heating on winter days e.g. when working from home.
The EV just charges off the mains at ~2 kW and we don’t drive much (maybe 25 kWh/week) so I hope to just fit that in as a solar sponge during the daytime.
Thank you!
Hi Gavin
With a flat roof, your solar installer is likely to recommend using tilt trays that will hold the panels at an angle of 10 degrees or potentially more. These can be placed facing any direction. Facing them north – or a few degrees east of north – will give the most energy generation per kilowatt of panel. But placing them east and west so the panels are back to back so the panels are like this…
/\/\/\/\/\/\/\/\/\/\/\
…except flatter, can let you fit more kilowatts of panels on your roof and generate more energy overall by allowing more panel capacity. Unless you have plenty of roofspace you are likely to find east and west is best and, after that, facing them all north. Placing panels so they face in several directions to try to match demand through the day is an option, but as they will likely be at a low tilt of perhaps only 10 degrees the benefit of doing this is not likely to exceed the slightly greater generation you’d get from placing them all facing north. And being able to install extra panel capacity by facing them east and west is likely to be best of all.
As for how much solar to install, I recommend putting as much on your roof as you are permitted and will fit without difficulty. This will increase the amount of solar generation in winter and on Melbourne’s cloudy days.
You could install a battery to meet your evening demand but at current prices it’s not likely to pay for itself in Melbourne. However, you may value its ability to provide backup power or you may simply want a battery because you think they’re cool.
If you have any questions, feel free to ask.
Hi Ronald,
Thanks for the quick reply, you’ve right away come up with a few things I had not considered.
First, perhaps how much I can install *will* be limited by the size of my roof. I’ve tried to do a rough calculation based off the plans (it’s a new house) and I reckon our roof is about 100m2. But there are 3 skylights up there as well as solar hot water (2 panels + the tank) so maybe only 70-80m2 of usable space. How much kW would that fit?
I had no idea about the /\/\/\ back to back method! With the tilt trays, why is such a small angle (10 degrees) used? Is it so the front row doesn’t cast a shadow on the row behind? Or is it more to do with wind loading? For Melbourne I assume the best annual output would be with 37-38 degrees of tilt but if I’m looking to maximise winter generation I was thinking even 45 degrees or something. Is that just crazy?
I looked into a battery (briefly) and do think they’re cool, but not cool enough to buy one yet. I will hold out for V2H one day 🙂
These days it’s not difficult to get 20% efficient solar panels. This means one kilowatt of solar panels will cover 5 square meters. Because they’ll be tilted they’ll take up a little less room, but in reality you’ll need more than 5 square meters per kilowatt. Some installers will use up all the available space if you ask them to, while others will want to leave space to access panels. If you do get panels that are packed in and hard to access, make sure you use good quality panels and a good quality installer so hopefully no one will have do work on them for a long time. As a very rough guess, you may be able to fit around 10 kilowatts of panels on your roof. Fitting that many may require placing them east and west.
Tilt trays placed on flat roofs often have a low angle because of wind loading. A second reason is to reduce their visibility from the ground. Ten degrees is generally considered the minimum tilt necessary for rain to effectively clean panels. If you had a lot of space but only a limited number of panels then facing them north and tiling them over 10 degrees would improve their output. But, using more panels — mostly back to back and facing east and west — can give you a higher panel capacity and let you generate more electricity overall, even though the amount generated per kilowatt of panels won’t be quite as high.
For most people there’s definitely no need to rush to get a battery. You can always get one later if you change your mind or they drop far enough in price. Convenient and easy to use V2H may be a way off, but I expect it will be practical at some point.
Thanks Ronald. I’ve looked at my last 12 months usage in detail this week and winter heating, morning and evening, is by far my biggest load. Way more than summer cooling and way more than charging the EV.
I can’t see a way to upload an image file here (?) but I shared it on LinkedIn here if that works: https://www.linkedin.com/posts/gavinmooney_heating-cooling-evcharging-activity-7057122033783951361-983n
But if I understand you right, you’re saying that the additional panels I can install if I go for a simple 10 degree east-west arrangement would probably still generate more energy at the start/end of day than if I try to arrange the panels at steep angles to capture the lower sun?
Yes, that’s right. Having more panels will result in more energy production than a smaller number of perfectly angled panels.
Hi Ronald – working through some quotes and panel arrangements with the installers now. I like your idea of the “concertina” panels as described in Option 3 in this article https://www.solarquotes.com.au/blog/solar-flat-roof-east-west-tilts/
But I was surprised our installer seemed to think it would involve quite a bit more labour than normal tilts. Is this normal? Also, far from being common, it’s an arrangement they’ve only done once before.
Our roof is in 4 sections so we would end up with 24 panels in total, but arranged like this:
Section 1:
2 rows of 4
Section 2:
2 rows of 4
Section 3:
2 rows of 2
Section 4:
2 rows of 2 (joined on short edge)
So perhaps it’s our roof that’s making it complicated?
He thought it might increase the labour by up to 50%. And lots of connectors, we’d need about 50 “MC4” connectors apparently.
Hello again.
If the concertina arrangement allows more panels to be installed then that will require more work. Also, the panels will have to be wired up as the installers go — or at least every second row will. But I couldn’t say how much extra work will be required. Your roof arrangement does sound a little complicated. It will come down to if it lets you fit extra panels and if you consider the extra capacity worthwhile.
Hi, there was an economical solution to the V installation (ie zig-zag, lifted centre at SmartEnergy 2023 but I cannot remember the company. Basically, you have a flat rail & low & high stands available in sizes up to 15 deg tilt. The long stand bolts to the rail & the panel clamps on the top. Easy install, & slope can be back to back as you want. Should be googleable!
Hi
I am on the verge 2-3 weeks from getting my solar system installed and have a direction question.
system will be 10.6KW 24 panels @440w each and 10kw inverter.
I have a large potion of roof that can take the system that is 5 degrees east of north so pretty close to perfect, sydney area. pitch 24 degrees.
But also have a west facing roof at 274 degrees from north with a 7 degree pitch that could take say one of the strings to help me produce later into the afternoon with the setting sun.
My largest consumption period is afternoon/evening so with the west facing panels would I grab a bit extra power? or no all panels on the north would work best?
The report generated by the solar companies computer has both the all north system or the 2/3 north and 1/3 west generating very similar kw per month data. 1-3 kw difference per month.
So question i have is what system should i go with in your opinion;
all north system?
2/3 north and 1/3 west system?
Thanks
Go 2/3 north and 1/3 west, you’ll get more energy later in the day when you need it.
We have a 3 kw solar system present. It was installed about 6 years ago on the advice of 3 installers who all said that 3kw was big enough! It patently isn’t ! Are we entitled to the government rebate if we put in a bigger system or add to the one we have ?
Yes – you will get the rebate on any panels you add – it will be included in the quotes you get.
*snap
Hi Peter,
1kW used to be normal and few people had enough money for 2kW, that was very well to do territory. When I could afford my first system 3kW had fallen to $12 000; just for the parts…
Nowadays a new inverter will have a new serial number and then you can claim new STC incentives on new glass for the roof.
13.2kW is the new norm and you can get that for the same $12 grand in a lot of cases.
Depending on where your old system is, if there is space for more, or if there’s a good case to get rid of old rooftop isolators, or if the network authorities will allow an expansion without bringing the old gear up to latest rules…. you might replace the whole system or simply add another one beside it.
I’ve never met a customer who’s complained they installed too much solar.
Hi,
We have two solar systems which are interconnected.
The 1st one was installed in 2016 – 20 panels 6.3kw with an ABB inverter,
The 2nd one installed n 2020 has 8 x 300 watt panels – 2.4 kWh with a 5kw Solis hybrid inverter & a 6.5kwh LG battery.
We had originally requested that the 2nd system have 12 panels but the installers decided on the day that they couldn’t add the extra panels even though there appeared to be space on the garage roof. They said the panels could not be installed close to the roof edge.
We are still hoping to add more panels to the 2nd system,
Can you recommend any solar installers who could provide advise re adding another say 4 panels?
This article is all well and good, but i have seen little reference to orientation and the Time of use charges. My thinking is that after 2pm when your electricity is 3 times off peak rates and it is on average the highest consumption period of a household, you should have a higher percentage of panels that would take advantage of the western sun so as to maximize the saving that can be gained.
Hi Geoff,
West is the new north for TOU tariffs, but really everywhere is the new north so long as it’s in the sun.
https://www.solarquotes.com.au/blog/roof-orientation-solar-australia/
https://www.solarquotes.com.au/blog/self-cleaning-solar-panel-pitch/
Intersting article! Particular how changing the orientation 10-20 degrees from Nth has minimal impact on annual generation.
The key benefit of rooftop solar is self consumption and reducing grid imports. (rather exports for feed-in-tariffs)
Generating electricity in the afternoon is beneficial as for most regions peak pricing starts from 2 , 3 or 5 pm and import rates become much more expensive. So more generation at this time reduces imports at peak rates.
The article focuses on benefits of afternoon feed-in-tariffs, in my opinion, incorrectly. (unless I have missed something)
Thanks for the well qualified feedback Jonathan,
I did a bit of an update on this subject and I’d love to get your opinion.
https://www.solarquotes.com.au/blog/roof-orientation-solar-australia/
Seeing as feed in tariffs are headed for zero (or even the dreaded sun tax) I’m keen to get the latest thinking on the subject.