The following is a very common question that comes in to SQ HQ.
“My roofline is North/South, so my largest roof areas face either East or West. I have been told that North Facing is ideal, but I have a tiny North facing roof! Can I put some solar panels on the East or West Facing roof (or both) ?”
Short Answer: Stick some (perhaps all) on the West!
Longer Answer: In terms of the amount of power produced, facing your panels East will produce exactly the same amount of power as facing them West. In either case you’ll generally take a 10-15% power hit compared to having them facing the ideal direction (North).
Is North always the best direction for solar panels?
So why do I say “probably West” as the short answer to the question?
Well, the reason I err on the West facing roof is because that part of your roof will get the sun later in the day. An East Facing solar array will generally produce its peak power at 10-11am. A West Facing array will produce its peak at closer to 2pm.
Most people use more energy later in the day. And most people want to use as much of their solar energy as possible, without exporting it. Why? Because at the time of writing most Feed In Tariffs give you less per kWh if you export the electricity than you pay for imported electricity. So most people will pay off their solar system quicker if they minimise exports.
Here’s a much more detailed explanation of how solar energy is exported depending on the time of day.
So if you face the panels West, and you are a typical family (in terms of electricity usage patterns anyway!), and your FiT is less than your retail electricity price, then West facing Solar Panels makes more sense than east facing.
In fact, if you live in a State with a really miserly FiT (hello everyone except those in NT!) then it may actually make more financial sense to face your solar panels West rather than North! To work out if this is the case you’ll have to get a good feel for when in the day you use electricity, then estimate how that will affect what % of solar power you export. Then you can use my solar power payback calculator to see which configuration pays back quicker.
Or if that sounds like too much trouble – you could always engage a good solar power sales person / installer to do the analysis for you. And asking them to do this is a great way to filter out the not-so-hot sales people out there!
Time of Use Electricity Pricing is Coming!
One more reason to consider West facing panels is that many people (me included) believe that in the near future everyone will be forced on to Time of use (TOU) electricity pricing where you pay differing amounts per unit of electricity depending on when you use that electricity.
For example Energy Australia‘s weekday TOU tariff costs 18c per kWh from 8am to 2pm, and a whopping 44.7c per kWh from 2pm to 8pm.
If you were on a similar tariff, it could make a lot of sense to push your solar power generation to later in the day, where every kWh of solar power you use is worth 2.5 times more!
The key is to find a solar installer or salesman that understands this stuff.
All this talk of Feed In Tariffs, TOU tariffs, and solar panel orientation can start to overload your brain when you combine it with trying to choose an installer and solar panel and inverter hardware. I feel your pain! The answer, as I mentioned above is to find a solar company that asks the right questions:
1) What times of day do you use your electricity?
2) How much do you use?
3) What kind of electricity tariff are you currently on?
So that they decide which panel orientation is right for you based on numbers (not a Wild Assed Guess!) and also so they can provide accurate payback calculations that take into account the ridiculously varied Feed In Tariffs in every state.
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Was told by an installer/sparky recently that West-facing cells get hit with heat coefficient losses (metal roof) because when the sun hits them, they are already hot from higher afternoon ambient temperature plus temperature of roof. East facing in the morning the panels are cooler so you will get less losses from heat de-rating…
Guess it depends too on size of system and the corresponding savings involved.
Most installers/suppliers seem pretty lazy and/or dopey/greedy when it comes to sun angle and orientation. They will usually just slap them on your pitched roof without optimisation for sun angle. Most sparkies seem too lazy/greedy to fit tilt frames, because they want to make $2000-3000 for only a day or two of work.
Had a bloke on my roof with me the other day and I have flat section of roof (about 40 metres square), and pitched sections of various orientation for the rest of the roof . Even though the flat section faces east, it would be best to fit tilt frames and then they would all face north. He wasn’t keen at all to fit them and suggested east instead. Although he said the costs outweighed the benefits…
Now I had a look at a figure with sun angles, orientation and efficiencies, and east-facing would be maybe 80% efficient (23 degrees pitch) ? Considering the Qld FIT of $0.44/kWh that would mean about $128/year difference per kWp. If I can fit 2 kWp on the flat section, that is $256/year. If based on $0.25/kWh charged for consumption about $73/year per kWp or $146/year for a 2 kWp system. Over 16 years (until 2028) for $0.44 FIT that’s 16 x $128 = $2048. For 2 kWp that’s about $5 000.
Even with no FIT and 10% increase per year for power starting at $0.25 kWh (2012) that’s $1 274 over 30 years per kWp.
Cost for tilt panels – DIY is around $60 (eBay), and around $85 installed per panel (based on one quote). So that’s $240-$340 per kWp (4 x 250W) so you’re up by $900-$1700/kWp for the extra expenditure (cash basis). For 2kWp that’s $1800-3400 return on investment over life of system or rebate period for ~$500-700.
Moral of the story – (pretty much) everything you are told is bullshit – you can only rely on your own research from informed sources. And do a lot of hours in the process.
A very important factor is not considered here… local clouding. In Tassy (where I lived) it clouded to the west on the mountain. Where I am now in SA it soon clouds in the morning and it is worth getting this kind of knowledge for the whole year for your site. from personal observation and talking to old blokes in th area and even ask weather people’s opinions and make an intelligent decision with all the factors onboard.
I live in Townsville, skin cancer capital of Austrlalia but I have a 3 degrees pitched roof and have mounted my string of 11 Qcells 235 W panels in two rows near the western end of my roof cause the morning sun is blocked by Mt Stuart Range and trees along Ross River. I was first easing for a reasonable pitch that I was first quoted on but changed and opted for the 11th panel. It seems from reading several of ur recommendations that I’m on the right tracks. However with a low 10 month rainfall and next to the main road and dirty fruit bats my panels get very dirty very quickly, what if any, can i do. Also would a cheap brand ‘x’ degreaser be Ok to spray them with before I hose them down. I have been brushing them with a horse hair broom while hosing them up till now.
Thankyou for your common sense answers on your webpages. God bless you too.
Hi Greg,
No degreaser – just water to hose down the panels – any additive is likely to leave a film which will reduce performance.
You need to use soap to remove bat poo etc, then make sure no soap residue is left on the glass.
Hope That Helps,
Finn
ElCheapo dishwashing liquid ~ under $1 per liter ~ is about the best all-purpose non-contaminating cleaner going; particularly for anything with a viscous base.
Hi,
I am in the process of getting Solar Panels installed on my roof. The front of my house faces north. The sales person suggested I install a 2.2kW system with 12 panels . The techs rocked up on my door step and informed me that they will not be able to fit 12 panels on the front roof (lack of roof space) and suggested that I split the panels- 6 facing west and 6 facing east. They have offered me a Dual tracking inverter.
I am now a bit worried about the efficiency and have read on multiple sites that it is ideal to install the panels facing the north. The techs have assured that they done similar setups(east and west panels) for other customers and the result was good.
I have been searching the web for reviews on a similar setup but have not been able to get a decent review
Does anyone have any suggestion?
I have clearly informed the installers that if the setup is not efficient in terms of power generation then I will not make the full payment and that they will need to relocate the panels.
Any suggestions would be highly appreciated.
Thank You
Note: Not sure if I am posting this in the right area.
Hi Nicholas,
AS long as you have a dual tracking inverter you should be fine. Yes – the west facing panels may generate about 15% less energy than if they were on the North face, so overall your energy yield may be about 7% down compared to all north facing. But… as explained in the blog post above you will probably save more money with some west facing panels because you will generate power longer into the late afternoon/evening when you are more likely to use it in the house and save approx 30c per kwh compared to exporting it at 8c per kWh.
Hope That Helps,
Finn
I was advised by a solar salesman that as I only had the option of an east or west facing roof option I should put half on the east side and half on the west side – from my research so far I thought the best panel only performs as good as the worst (e.g. if some panels are shaded) therefore with this option would I not loose on a double whammy basis – not getting peak output unless the sun is directly overhead? (Cairns QLD)
(In addition to the above) The Aurora 3.6 outdoor Inverter was MC 1V was quoted.It may also be of interest than some Home Insurance companies will no longer cover solar panels or Solar hot water units not fixed directly onto the roof .Tilted frames are no longer acceptable – definitely an issue in cyclone prone North Queensland.Many thanks to you and your site.
Dennis – splitting the arrays between East and West is good advice. It spreads out the generation more throughout the day.
But…
You are correct re: it only performing as well as the best panel. So you have to do this if you plit the array:
http://www.solarquotes.com.au/blog/solar-panels-on-roofs-facing-different-directions-then-you-need-to-do-this/
We have east west panels 7 either side with dual input inverter, generates about $500 per quarter summer months, $200 winter months (50 cent deal). Far better performance than what I expected
Crunch Time !! I have an existing array SB 1100 with what I believe are 6 suntech panels using the only available north facing roof area. It would be my intention to install a SB 3800 with the maximum number of panels allowed Hanwha) – half facing east,half facing west.(no shade problems).We have 2 X 250 litre hot water units (3600 Watt)(house & Bungalow – is it feasible to put these on timers to only heat during daylight hours ( one AM one PM ) i realize they would still take power from the grid.Many thanks Finn
Hi Dennis,
Yes perfectly feasible to get the sparky to put in a $50 timer that only allows the water to heat during the day.
Also you may want to consider heat pumps for your hot water: http://www.solarhotwaterquotes.com.au/solar-heat-pumps.html
Finn
Why is it you say a timer is $50 yet everyone is quoting me $150 to $200 to add to a solar system.
Hi Betina
A timer only costs around $50 but there will be a charge for installing it.
im part way through redoing my whole solar set-up. everything from replacing the cabling from the PV array to the controllers (was ordinary 240v house wiring) with proper rated PV cable. my issue is i have limited space facing north that is usable for mounting panels. am able to fit 5 panels in the space provided, so i made the call to mount another array on the west side. should i just put them all on the west facing roof or is splitting them up like that ok?each array has seperate cabling joined at a ‘j’ box prior to going to the batteries/ controller. I also have purchased 200w panels as 90% of the existing panels are 200w mono’s, there are however 3 165w poly panels in the mix. should i mix and match them or replace these with more 200w ones?? thanks
Hi Justin,
If you are going to split the array over two roof areas facing different directions then you should do this to maximise your output:
http://www.solarquotes.com.au/blog/solar-panels-on-roofs-facing-different-directions-then-you-need-to-do-this/
The 165W panels will reduce any 200W other panels in the same string down to 165W.
Hope That Helps,
Finn
I have solar panels with east west configuration with a twin input inverter at Wynnum West. Performing well above what I had thought I would get. There are 14 panels 7/7 about 200watts each
I live in Adelaide and have a really strange roof. I have 2 panels on 45 degree tilt west roof wired to Rennai gas and these seem to work quite efficiently so I am not concerned about these. However the electricity panels are a different story. I have 9 panels (1.62 Kwh system – 3Kwh inverter) facing west on approx 10 degree tilt roof. I tried to put 9 on the north roof but they wouldn’t fit. Now i am stuck with low solar generation and I want to change this around so the 9 panels work better. So the choices are 1) relocate about 5 panels to the west facing 45 degree roof (near the gas panels) and leave the other panels on the 10 degree west roof (this is all that would fit) or 2) install a frame to increase the tilt on all 9 west facing panels or 3) add 5 panels on the west facing 45 degree roof as there is extra capacity in the inverter or 4) add 4 panels to the 45 degree north facing roof as there is extra inverter capacity.
I hope this is making sense and someone can tell me which would be the most efficient in terms of solar generation and also capital value.
What should i do? Thanks a million for any advice you can give
Kim,
In Adelaide, panels on a 10 degree roof, west facing will give you 88% of the power of panels on a perfect North Facing 30 degree roof.
In other words, the absolute best you can hope to get is a 12% improvement by moving the panels. It is not worth the expense.
If your panels are underperforming by more than 12% compared to North facing panels then there is another problem with your system.
THis may help:
http://www.solarquotes.com.au/blog/how-to-work-out-if-your-solar-system-is-performing-properly/
Finn
I just want a simple answer. Which solar power company can I trust to do a good job at a reasonable price. I’ve been trying to find out for some time now and am still stumped!
KBO 18/12/14
Hi Kevin,
Let me know your postcode and I’ll recommend someone. I’m assuming you want a simple Grid Connect system?
Finn
My roof faces south south/west with a 10 degree pitch. A solar company I am looking at going with has said I don’t need to tilt the panels, just add 2 more panels for equal efficiency to an optimal north facing pitch. Does this sound right?
I don’t know where you are (it changes with latitude) – but assuming you are in Sydney a SW facing roof at 10 degrees from horizontal will produce about 82% compared to perfectly oriented panels. So to make up for it you would need to increase your array size by 25% to compensate.
Hi Finn, Sunshine Coast SE Qld.
In the Sunny Coast, you’ll get about 86% compared to North facing – so you would add 16% more panels if you wanted to make up for the loss.
Hi Finn,
My roof is facing northeast/southwest. I use a lot of electricity during summer afternoon. I’m looking for setting up a 5KW inverter with max output around 5.8kw. I ordered 24pcs panels. I can order more to compensate the efficiency loss if facing southwest.
What’s The best way to allocate these panels? Half panels facing NE and half go SW? Or Most panels go NE, some panels on SW? All installers I asked prefer to put them all facing northeast.
It depending on your location and roof pitch, but expect approx a 4% loss for NE and 20% loss for SW facing panels compared to N facing.
You can get exact numbers with these tables:
http://www.solarquotes.com.au/blog/wp-content/uploads/2012/12/CEC-guidelines.pdf
SW panels will give you more power later in the day – and yes it can be a struggle to convince installers to do this – they are pre-programmed to only maximise total kWh.
If you split them 50/50 make sure you read this:
http://www.solarquotes.com.au/blog/solar-panels-on-roofs-facing-different-directions-then-you-need-to-do-this/
Hope That Helps,
Finn
Hi Finn,
I’ve received a quote for Hareonsolar for 4BB HR- 250P-18/Bb solar panels 5kW system.
They say that this is a Their 1 panel and is highly rated.
What is your thoughts regarding the panel.
Lloyd
Hareon is indeed a Tier 1 manufacturer so they should be a safe bet.
Hi Finn
Looking to purchase a 6 acre block in Kyneton Victoria which has the road entry on the west side and the views to the east towards Mount Macedon. So its and east/west running rectangular block essentially. We would want to build to take in the views from the living areas at the back of the house. The house being a long rectangle with most roof space running east and west. Given what you say would we be best to put panels on the east and west sides of the gable roof? Also maybe build a deep veranda on the east and west sides for the hot summer morning and afternoon sun?
cheers
Hi Karen,
A 50/50 split of East and West facing arrays with a suitable inverter is a great way to flatten the solar generation curve and self consume more of your solar.
Building your home to keep out the summer sun and also to let in the winter sun is super important – more info on this here:
https://www.solarquotes.com.au/energy-efficiency/thermal.html
Hope That Helps,
Finn
Hi Finn,
I am looking to invest in a solar panel system. I live in the southern highlands of NSW postcode 2578. Do you recommend any reputable company’s in my area?
Kind regards,
Andrew
Hi Andrew,
Off the top of my head 3 really good installers who are based fairly local are Scott at Australian Solar Designs in Kiama australiansolardesigns.com.au, Phillip at Living Power livingpower.com.au (Smeaton Grange), and Kangaroo Valley Solar http://www.kangaroovalleysolar.com.au
Hi Finn
I live in Perth. If I put panels facing WNW what would be the best inclination to mount these panels. Would it be steeper then 31deg due to the sun being lower in the sky? Also any reputable companies in Perth?
Regards,
Stewart
20-30 degrees from horizontal will get maximum year round energy if your panels are WNW facing in Perth. Steeper will actually lose energy yield overall.
Hi Finn,
I do also live in Brabham, Perth and my panels need to face the west what would be the best indication to mount these panels?
When facing West in Perth, the flatter your panels, the more energy you’ll get over 12 months.
At 10 degrees you’ll get 88% compared to the optimum orientation (30 deg north facing).
At 20 degrees, 87%
at 30 degrees 85%
At 40 degrees 72%
So any angle between 10 and 30 degrees from horizontal will work well.
Hi Finn,
Location is wollongbar nsw
We have a E W pitch roof at 30deg.
Both sides are approx 19mx7m
After installing a grid connect system (not expecting any FiT) initially until battery prices come down.
After thoughts on an all west facing setup as our house is empty from early morning except weekends and not home until afternoon
Thanks
It absolutely sounds like west facing is the way to go for you.
Expect to lose about 15% of your energy compared to North facing, but more than make up for it in self consumption $ savings.
You should be able to still get a Feed In Tariff – this tool will show you the local retailer offers:
https://www.solarquotes.com.au/energy/
When I pop postcode 2477 in there I see FiTs from 6c to 10c.
Hope That Helps,
Finn
Hi Finn, there is a lot of talk about East west split but what about a North West split, is that possible ? I will be building a house on the Fraser coast QLD that is true North facing with not a lot of roof space at North. I’m thinking the morning sun is fairly useless to a working household unless you have a pool to run for 6 hours a day so why couldn’t you have a NW set up? I’m guessing a NWE 3 way split is not possible due to needing 2 even amounts of panels.
Hello Sash, Ronald here.
If you mean an east-west split on a single string, I wrote about that here:
https://www.solarquotes.com.au/blog/an-eastwest-spit-of-solar-panels-on-a-single-string-can-work-well/
I suspect that on a 15 degree roof losses wouldn’t be too bad, but I don’t know of anyone that has tried it, so I couldn’t say.
Another problem is cloud apparently helped the system in Germany in the article get a good result and there is less of it on the Frazer Coast than around Kaiserslautern. I don’t think it has rained on the Frazer Coast for two months.
Now that panels are so much cheaper than they used to be, a north/west split on a single string wouldn’t necessarily be crazy from the point of view of wasted panel capacity, but since inverters have fallen in price as well it probably makes sense to get an inveter with 2 MPPTs or if you want panels facing three directions you could use more than one inverter. Another option is would be to use microinverters or DC optimisers or panels with panel string optimisation.
Hi Ronald, thank you for your reply.
Its probably more like 6 months for any decent rain but it sure is making up for it now. Its been raining for the last 3 days and a few more to come apparently.
So in theory, an uneven number of panels with microinverters could be placed in all 4 directions and still work ( not that you would bother facing them south) because they are all separate units linked straight to your mains power?
Thanks in advance.
Yeah, I heard the area is in for a ridiculous and dangerous amount of rain.
And yes, with microinverters panels can be placed in any number of directions desired without having any effect on each other.
The same goes for panels with panel string optimization, although I recently learned that the first generation of Jinko’s Maxim optimized panels are no longer available because they interfered with TV reception, but their generation 2 panels without this problem will be available early next year.
Hi, I have been reading your posts and replies for a while now and I have taken into account your recommendations and even though we live in a forest in Woodend, Vic we do have shade issues, so we were left with north and west, so we have 2 separate systems, we ended putting 3.2kw on our North facing garage and another 6.5kw (oversized) with a 5kw invertor onto to our house facing West, This has worked out very well for us, I was tempted to spit the 6.5kw PV array but because of shade on the East side decided against it.
Hi Finn, Ronald. A tweak on the east west issue.
I am building a 10m x 10m shed near Goolwa, SA. The shed axis is N-S so the roof panels face almost exactly E-W. It is an American Barn design, 11 degrees roof slope on the outer bays and 30 degrees roof slope on the middle one.
Own use power will be for a holiday shack so only intermittent usage maybe 3 months per year, likely a fair amount of power going back to the grid.
So, is it better to put the panels on the steeper roof or the flatter one? I plan on a dual input inverter to handle the 2 arrays. The CEC design guideline table reckons with a 90 degree azimuth 87% efficiency at 10 degrees slope and 82% efficiency at 30 degrees. But is it that simple? Does this account for the extra morning/evening own use I would typically have where the 30 degree panels would effectively extend my solar day? Also, the East facing array would get to its max power while cooler so should be a bit more efficient than the west? Or do I put panels on all 4 faces and get a 4 input inverter or even go to micro-inverters?
I’m interested to hear your thoughts on where to put the panels and also any thoughts on batteries in a situation like this (I await the announcement on the battery subsidy from van Holst Pelikaan with bated breath). My goal would be zero bills without overdoing the capital expenditure. cheers, Iain.
Hi Iain, Ronald here.
You can use the PV watts site to check output of panels at different tilts and orientations and takes into account the local climate:
https://pvwatts.nrel.gov/
You’ll have to use data for Adelaide or Mount Lofty but that should still be fairly accurate for Goolwa.
If you put panels facing east and west on the 11 degree slope roof you’ll generate more electricity through the year but on the steeper 30 degree roof the output will be more constant through the day which will help improve self consumption by a small amount. My guess is you will be better off with the panels on the gentler slope since most of the solar power will be sent into the grid for the feed-in tariff. Looking at the results.
Over one year 1 kilowatt of panels will generate:
East 11 degrees: 1,378 kilowatt-hours
West 11 degrees: 1,312 kilowatt-hours
East 30 degrees: 1,338 kilowatt-hours
West 30 degrees: 1,201 kilowatt-hours
So if the panels are put on the 11 degree slope they will generate 6% more kilowatt-hours over a year. My guess is this is worth a small decrease in self consumption. If helping the environment is important to you then go with the extra output reduce fossil fuel generation by 6% more.
There is no point in putting panels on all 4 slopes unless you goal is to build a large system and you need the space.
Thanks Ronald. Panels on the flatter areas it is!
I now know where to put the skylights on the shed roof (and where not to put them)
cheers
Hi Finn
I have a 1.5Kw west facing system installed 10 years ago is South Australia, I’m looking to add a 10Kw system, and yes i know i will lose the 50c feed in tariff – which is a completely other question but lets keep it back to the blog post
My question is with the feed in limit of 5kw is it still worth putting the new system on the west, or in this situation splitting will be better.
Also is it possible to still use my old systems (which give max output of 1.2kw) if its behind something like a fronius smart meter to limit both new and old system to 5kw ?
10 kW of panels on the west with a 5 kW inverter will work really well to maximise late afternoon power production which is the biggest stress on the grid. It will also help when SA is forced onto Time Of Use tariffs which charge more from 3pm.
So – if they’ll fit I’d whack 10 kW on the east.
You can keep your old system – but you’d have to limit the new system to 3.8 kW export or zero export limit the old system – which may not be possible with a 10 yr old inverter.
I’d remove the old system an put in on Gumtree.
Finn
Hi Finn this is a great site, so much info.
We live on the Mid North Coast postcode 2430 Black Head Beach
Our roof faces 340 degrees NNW and 250 degrees WSW about 30 degree pitch
I am thinking of a 6.6kw system.
We don’t use much power other than the fridges (two) before 11 am when the pool pump (multi speed) kicks in and runs for 2.5 hours, then another 2.5 hours from 2:30PM.
When on holiday we have a base usage of about 12kwh per day including the pool pump.
When home it is about 24kwh per day in winter with the heat pump running 11am till 10PM, we are home most days.
It is 21.5kwh per day in summer with the air con on in the afternoon and evening.
The rest of the year we use about 18.5kwh per day.
We can fit all panels on the NNW roof if needed and up to half on the WSW roof. Should we have a string on each of the two available directions The inverter has two strings. Can each string be a different size? If so what percentage split would you suggest?
Hi Douglas, Ronald here.
The NNW roof sounds like the best location for your solar panels. If you can fit all the panels there is no point in using the WSW section of roof.
If you have 3-phase power then I recommend installing more than 6.6 kilowatts. Your electricity consumption is well above average and it will be very useful if you get an electric car in the future. If you have single-phase power, as most homes do, then it can be difficult to get permission to install more than 6.6 kilowatts in your area, but you can check with your installer if it’s possible.
If you can install a large system then putting panels on your ENE section of roof is fine. They will provide power through the day and will help provide heat on winter mornings.
Thanks Ronald
I can fit more than 6.6 on the NNW roof and am looking at a 7.9kw system with a 6 kw inverter. I think this may be the go, not quite as much bang for the buck to start with, but will only take approx two months more to pay for itself and make a battery a more possible solution when they are much much cheaper.
As to electric cars, it would seem likely that if they become popular you will probably forced to have home solar to own one. Charging millions of electric cars off the grid would cause rolling brown outs without substantial upgrades to infrastructure and it has to be low emission or what is the point in just exporting pollution etc to where the power is made. Personally I think we need something better than electric cars as we know them. Certainly not cars as we know them, but some better innovation.