If you’ve decided on panel-level optimisation, which is the better choice, microinverters or optimisers?
Good grief this article is going to get me into trouble with some solar installers. Why? Because by the end of it I will give my humble opinion on whether microinverters (e.g. Enphase) are better than DC optimisers (e.g. SolarEdge or Tigo).
Please let me be very clear. This article is not saying microinverters or DC optimisers are a better choice than a standard central string inverter. That totally depends on your situation.
If you have an unshaded roof, facing one or two directions then a conventional string inverter system is a very compelling choice.
However, if you have a multi-faceted roof and or shading issues, then individual panel optimisation is almost essential. Your choice then becomes whether you achieve this with micro-inverter or DC optimiser technology.
But first – let’s get back to basics and explain the jargon I’ve just hit you with!
(If you prefer graphics to text this post is published as an infographic here)
The 3 ways you can connect solar panels together
1. String inverters
The traditional and most commonly used method is to use a single (string) inverter. On the upside it’s low cost, there’s a huge variety of products available and the technology is well understood.
Power is distributed at high voltage DC (typically 200-500VDC) to the inverter where it is converted to 240V AC. On the downside, because all the solar panels are connected together in series, individual panel outputs are not optimised. If shading, soiling or different temperatures occur the entire output can be dramatically reduced or even stopped.
A conventional system with a string inverter (image: Enecsys)
This is where “panel level” optimisation can help.
There are two primary methods used to achieve this that we will explore today– power optimizers (also called DC optimisers) and micro-inverters.
2. Power Optimizers
Power optimizers essentially split the traditional string inverter into two separate parts:
A solar system using Power Optimisers (image: Enecsys)
The panel optimizer is attached to the solar panel and thus gets the benefits of panel level optimization under a wider variety of conditions. Different manufacturers each claim different advantages and some partner with panel manufacturers to factory fit them.
The power generated is transmitted at high voltage DC (typically 200-500VDC) and the inverter, typically wall mounted, does the DC to AC conversion. Therefore you get the benefits of panel level optimisation and the cost savings of using a single string inverter.
3. Micro-Inverters
Micro inverters simply take all the functions of a string inverter and miniaturise it to solar panel level. Consequently, each solar panel has its own integrated optimizer and inverter attached either on or under each individual solar panel on the roof:
A microinverter based solar system
The power generated is transmitted at 240V AC from each micro-inverter and connected in parallel, then connected in directly to your switch board. Different manufacturers each claim different advantages and have a few minor twists on the theme, but the principle of operation remains the same.
Pros and Cons: Micros vs Optimisers
We have taken a look at the key issues that differentiate micro-inverters against optimizers and listed them below for you. In all cases, we are comparing to the better/high quality products because in our view, low end inverters, no matter what type, are a nightmare to be avoided!
Efficiency
As a general rule string inverters are typically marginally higher in efficiency. However, your overall system efficiency (yield) should be slightly higher with optimizers or microinverters because they optimise individual panel output. The difference in claimed efficiencies between optimizers and micro inverters is so little, it’s barely worth considering.
Draw.
Installation
Optimizers require a single inverter to be installed and DC cabling d protection equipment on the roof. Micro inverters do not and instead, use plug and play connectors to install so from what I hear they are faster. However, if your module already has an optimizer fitted then you are installing single inverter only plus the cabling, this option would be marginally faster. Theoretically, the efficiency of DC or AC transmission from the roof should be about the same, assuming standards are followed.
Draw.
Flexibility & Expansion
Because optimizers need to be designed to match the “maximum panels per string” on string inverters, the design parts takes a little extra time. I also note that not all inverters work with all optimizers, so you need to get some product familiarity training, although there are some neat tools to help you.
Micro inverters on the other hand only need to match the power output of the panel and then are only limited by the capacity of what they call “AC branches”, or to the layman, the power limit of the AC cable and plug system. In most residential applications you won’t hit this limit.
Additionally, if you want to add more panels later, a micro inverter system can easily accommodate this as long as you don’t reach the AC Branch limits, and you can add them one at a time if needed. Optimizers need to be matched to the string inverter limits, so that’s a harder boundary.
Win to micros.
Scalability
When you consider larger, commercial installations the theory is that optimizers have two advantages. Firstly, you can go to larger string inverters which get cheaper as they get bigger. Secondly, three phase or “double optimisers” which can take inputs from two panels offer further scalability benefits.
Putting aside the design and installation complexity (compared to micros) I think optimizers may offer a very slight advantage in terms of capital cost due to scalability.
Win to optimizers.
Battery Compatibility
Batteries charge and discharge DC electricity. So batteries should be cheaper and easier to integrate with Optimisers, because they keep the DC wiring all the way down to the central inverter. Certainly the Tesla Powerwall is designed to integrate out-of-the box with Power Optimiser company Solar Edge’s inverters.
An microinverter system runs on AC, so battery integration is always going to need an extra battery inverter to “AC couple” it into the system. This will make battery integration more expensive with microinverter systems if you are buying your solar and batteries together.
If you are planning on retrofitting batteries later, then you’ll need to buy a battery inverter anyway, so it should be no more expensive to retrofit batteries to microinverters or DC optimisers.
Win to optimizers (just).
Robustness
This is a tricky one. On the one hand the logic of having fewer parts on the roof (just the optimizer and not the inverter electronics) is pretty sound. Intuitively, this would suggest a higher probability of reliability to optimizers. However, with the benefit of hindsight in the market I don’t see evidence of any major differences in failure rates (excluding crappy micro inverters). What we also see from the top micro inverter guys is very high volume manufacturing and intense attention to automotive level quality assurance.
It’s also the case that in a micro based system, if one unit fails, the rest of the system keeps on working because there is no single point of failure. In an optimizer based system, if the (single) string inverter fails, the whole system shuts down and in some cases if a single optimizer fails the string goes down too. Having said that, replacing a single inverter in the garage is easier than climbing on the roof.
Theoretically optimizers should be better, but compared to top end micros and overall, I don’t see it, especially when redundancy benefits are factored in. Optimizers have two potential points of failure– the optimizer and the inverter- compared to micros single point and I think that separates them for me.
Another factor to consider is the reliability of the solar panels that the inverter or optimiser is attached to. Potential Induced Degradation (PID) is a failure mode of solar panels that is caused by high voltages across the panel and may not show up for 5-20 years after installation. Microinverters keep the panels at a much lower DC voltage than optimisers and so the theory is that this will reduce the chance of PID in the panels. PID is one of the more common causes solar panels failing in the medium to long term.
Win to micros.
Safety
Around the world the risks of High Voltage DC continue to be debated. When everything is done perfectly, great gear is used and maintenance is regularly conducted, HV DC is just fine and very efficient. However, the reality is that often isn’t the case and so rooftop safety is a growing issue. HV DC and 240V AC both present electrocution risks, but HV DC is more prone to creating fires when it all turns bad.
The major optimizer manufacturers almost all talk about their roof mounted units being able to recognise fault conditions and having the capability to isolate individual panels in the case of a fault so even though the HV DC cabling is still present they seem to have that in hand. What I don’t like is that you still need DC isolators which are the number one cause or problems in Australian solar systems. I also note that some optimizers require an optional device to enable this functionality in some circumstances, leaving room for error.
Micro inverters don’t let the DC out; it’s converted immediately to 240AC. Generally speaking it’s also true that electricians are more familiar with AC. Theoretically based on of all of the above, the risk is slightly lower with micros I think.
Win to micros.
Price
The general market price of an optimizer system (including the inverter and DC protection gear) is lower than most micro based systems although the gap is closing rapidly. So ignoring everything else, optimizers win today.
However, I don’t think that tells the whole story when it come to the end customer because they want reliability, performance, adaptability and the lowest cost of ownership, although they might not say that. They don’t want hassles and prefer flexibility. The installation cost was a draw but there’s arguably a bit more design and specification time required with optimizers. Flexibility went to micros but scalability to optimizers so let’s call that quid pro quo. Lastly you have to factor in reliability and safety issues, which was a close call but I think went to micros.
So on raw price, a Win to optimizers.
On lifetime, overall price, a Win to Micros.
The Result
Based on this assessment and our reviews of as many other assessments we could find, I don’t think the jury is out on whether optimizers or micros offer distinct advantages over each other. They each show some benefits and advantages but on balance they almost match each other.
It therefore becomes a subjective matter so I’ll just give my opinion and leave you to make up your own mind too. I think lifetime cost, flexibility and simplicity make sense so I would give it to micros. But if a DC coupled battery was on my wish list, that would tip the balance to optimisers due to the cheap integration. What about you? Let rip in the comments.
Update: November 2018
I’ve recently changed my mind on this. Most people have a relatively simple roof (panels will face 1 or 2 directions). They also often have one or two shade objects such as stink pipes, aerials or chimneys. The most cost effective option in these situations is a string inverter with Tigo optimisers only on the shade-affected panels. This way you get the cost benefits of the string inverter and the optimisation on only the panels that need it at an extra cost of only about $100 per optimised panel.
If microinverters ever get as cheap as string inverters (as Enphase have been promising for a while now) then I would recommend microinverters. But at the moment they are still add about 20% to the system price.
About Finn Peacock
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I have two new smart meters and they would not connect me for feedin until I consolidated them to one meter. I could not get any sense from the power company so I went to the ombudsman who gave it a lot of time. In the end, they said it has to be a net feedin calculation and requires one meter. In this day and age we can’t add two together. Has anyone else had this problem?
lol!…..Dunno that I’d be using this sort of comparison:- ” and intense attention to automotive level quality assurance.”
I’ve just spent four days and several hundred dollars bringing up to scratch a relatively low-mileage car (Ford), including valves/tappets, timing, carby-kit, etc. (all the ‘normal’ ~ periodic ~ stuff), and then still had to take it down for a dyno-tune/exhaust-analysis.
…..and it wasn’t even up on a wet and blowy roof!
Ford? Fix Or Repair Daily…First On the Rubbish Dump
Also reminds me of:
Fiat: Fix It Again, Tony.
Lotus: Lots Of Trouble, Usually Serious.
Anyone got any others?
Hand On Little D*ck Every Night.
Ford first on race day
Holden, Holes oil leaks dents engine noises
Holden: Barely holden together.
FIAT First in alltroubles
LUX FIAT = Let there be light, so FIAT = Let there be
ps. I STILL can’t see a better ~ and virtually bomb-proof ~ piece of technology than the ‘standard’ grid-connect inverter, and swear by my much-maligned Aero-Sharp which ‘does it all’ with panache and nary a hiccup since the early problems with failing voltage-suppressors was fixed. (For free, without a haggle and apologies for the inconvenience.)
The still-perfectly-operating replacement took me about TWO MINUTES to install.
My only gripe is that ~ despite several requests ~ none of the whizkids here and elsewhere have come up with a way of circumventing the ‘anti-islanding’ loop so that it can be used in a stand-alone situation.
It performs ALL the tasks the pricey alternatives do, and ~ according to the published figures ~ does so significantly more efficiently.
AND I already own it.
(any expert views welcome: happy to pay for your time: jasw-AT-y7mail.com )
G’day Finn,
Thanks for the timely and interesting article mate!
I have been researching this for some time, and in fact, the desire to integrate storage has delayed me installing any solar up to this point. Though given Elon Musk’s announcement about Powerwall and the continued reduction in costs of systems now, I am now very seriously considering my options.
In my opinion, one critical aspect in the analysis should be the likely loss(es) that will ultimately occur in any DC-AC-DC conversions that will invariably occur with a micro-inverter system. When you take this into account then a DC-DC coupling of say a SolarEdge solution is probably a winner, though I don’t discount some of the points you raised above.
Anyway, with this in mind, my house is wired for 3 phase so I am unsure as to whether the SolarEdge inverter or storage interface module would provide any dynamic load sharing across all three phases or whether there is a need to have additional components to facilitate this. I am not sure if the Enphase solution has a buggery box to facilitate 3 phase load sharing/balancing either.
My end solution is complicated by the fact that I wish to run in-slab heaters, which on average consume about 80-100Kw per day. I would love to run these directly from solar during the day but I recognise that even a 15Kw system (as much as my north facing roof aspects will accommodate) will not cut the mission during winter months …. though I could use the grid to build up a credit during summer months upon which to draw down at a later date. In addition, I am just now looking at EVs or PHEVs to potentially improve the potential ROI of the overall system also.
Finally, there is perhaps another option that should be mentioned here, though it is hard to beat optimisation at a per module , but it is the new range of hybrid inverters that are coming onto market. The Fronious Symo Hybrid inverter is a case in point here and it is also a preferred solution for the integration of Tesla Powerwalls I notice. Cheers Peter
The AC battery is fundamentally a bad idea. It is simply a battery with a rectifier to convert the AC to DC and inverter that will concert the battery DC to AC. It will result in at least 5% additional energy loss compared to a solaredge/tesla battery system. Enphase AC battery has zero chance of being even close to the cost of the powerwall unit on a per kilowatt basis. It also adds equipment cost and reliability issues. Tesla selected the solaredge process based on the technical and economic advantages.
As installers we used enphase micros for years before switching to optimizers almost exclusively about 12-18 months ago. Over time we’ve had many micros fail causing downtime and loss of productivity for our customers and requiring time from us to go out and replace them. Not a huge issue, but definitely not ideal. On the other hand, we’ve never had one optimizer fail. This gives optimizes the win for efficiency to me. Is this consistent with other installers’ experience ?
Also, Finn, in your opinion how does the solaredge SafeDC feature improve the safety of optimizers compared to micros?
Thanks! Dara
Hi Dara,
That’s interesting, thanks.
1) Do you know what the failure mode of the micro failures was?
2) How recently have you had to replace one and what model version was it?
Finn
Hi, Finn
Just as we thought we were close to a decision on our new string solar system, one company raised the possibility of micro-inverters, especially given that we have some shade issues on a well-treed block. You’ve said elsewhere on your blog that if the prices are close you’d opt for micros but I’m also conscious of the comments about extreme climate stress as an issue for micros. We are in SA where summer temps of 40+ are increasingly common. Your thoughts please.
Regards
Doug
Personally I’m pretty happy with the reliability of good microinverters (like Enphase) even in Adelaide.
I’ve had micros on my roof for 2 years and they’ve never stopped producing power, even through the heatwaves.
I think Enphase are warrantied for 12 years in Australia wheras most central inverters are 5 or 10 year warranties.
Enphase have a case study from 170 Enphase installations in the Adelaide heatwave of 2014 here:
http://www.solarquotes.com.au/blog/wp-content/uploads/2015/08/Internal_Temp_Tech-Brief_AU.pdf
Good article. One caveat. In 10 years, batteries will indeed be affordable for almost anyone to go completely off grid as long as they have space for them. Utilities are fueling batteries as well as they continue to increase thier “grid” fees. Here in san diego I am already paying $45/mo just for being able to use the grid even if I use 0 electricity. In 10 years I am sure that same fee will be between $75-$100 because those executives dont want to take a pay cut so they will need to keep revenue and net high even if it destroys the business later. They dont care because they probably wont be there anyway and could liquidate their stock long before it happens.
That means that micros are a bad choice even if their own battery is cheap for the simply fact that every time you convert you lose a significant amount of power. For micros you will be coughing up about 5% just for conversions. No such issue with Tigo or Solaredge although I am not a fan of solaredge because of their proprietariness. I am rooting for Tigo but they have some issues to iron out.
I have a few questions for you:
Can a string inverter system be converted to a micro system and would that affect the feed in tariffs in Victoria even if no extra panels are being added?
Also if micro’s are individual can they be added (as in more panels) without affecting the feed in tariffs?
One last thing if being able to add capacity to an existing system and not lose your current feed in tariff by creating a what is essentially a new parallel system is possible (as I understand it) up to a certain kwh limit (usually <10kwh), is it possible to add a micro array as the parallel system, when you have an existing string inverter system already installed, e.g. is it possible to have a hybrid system? If possible would that be a good idea or fraught with bad karma?
I ask the last question in the view that the extra panels would have to be installed on the east west facing sides as its a small roof and the north facing is already filled up and as I understand it reading your website, micros would be better (more efficient) for the extra panels having to be fitted to the other facings (based on efficiency, redundancy, shading and east west facings having peak times/lower light times which micros have better output for in these situations being individual, instead of series)
Adam, generally you can change your inverter without losing a high feed-in tariff, as long as the total capacity of the new inverter or inverters is not larger than the old one. So you could replace a string inverter with microinverters provided the total capacity of all the microinverters was equal to or less than that of the old string inverter.
If you have an existing string inverter system and add panels using microinverters that counts as adding to the total inverter capacity and if you have a high feed-in tariff that will cause you to lose it.
If you have a high feed-in tariff and want to keep it you can’t add any additional inverter capacity that is connected to the grid. But it is possible to add solar panels and inverters that aren’t connected to the grid. For example, you could use solar panels to run an off-grid pool filter or hot water system, or whatever.
If you are not on a high feed-in tariff, or simply don’t care about losing it, then your options on how to increase your solar capacity are more open.
Hi
I was wondering with the high feed in rates can I install a larger capacity system and export limit to the approved system.
Therefore can use the additional non feed in power for my home and maximising the feed in to the grid.
I’m sorry Allan, but any increase in inverter size will result in the loss of a high feed-in tariff. But depending on where you are it may be possible to increase the number of solar panels you have and keep it. You may be able to increase your panel capacity up to 133% of your current inverter capacity. Unfortunately, you can generally only do this if your inverter meets current standards and it is likely an inverter that is receiving a high feed-in tariff is old enough not to.
I was just wondering, you say if you want the powerwall, it would tip the balance towards optimizers, because of the cheap integration.
But doesn’t the powerwall come with its own built in inverter to be able to be hooked into AC systems so it can not only be re-charged by solar energy but also by off peak mains energy for load shifting purposes as well?
In that case it should work perfectly well with micro inverters as well out of the box making it just as a viable option, unless there is something I am missing?
Hi Adam, Ronald here. This is an older article, so it is referring to the original Powerwall which didn’t have a built in inverter.
https://www.youtube.com/watch?v=JHCrdtIvD3I&t=3s
Six was failed.
Are you sure that electrolit capacitors attached backside of a solar panel can work for almost 25 years? … Nonsense.
there is ~450 components in a microinverter. At enphase you should buy an extension of monitoring to be able to check every panel, so if something is broken, the system will produce and you will not notice it, if u did not bought it…
There is no white paper (like sunpower did with their panels), that would show how much test cycles needs for micros to fail.
Hi GP.
Pretty old story in your link – 2010 installation – so it could be fair to say that their product might have improved a bit since then as they are still here and still offering a very useful warranty.
The expected lifetime of an Enphase microinverter is 25 years, the expected life time of a string inverter is about 12 years if you are lucky. So factor in the replacement cost of the string inverter halfway through the life of your system and the economics for DC optimizers changes significantly.
Hi,
1) For a roof with scattered shading issues, would you recommend Enphase Microinverter or SolarEdge Optimizer? Why?
I have read and asked around regarding the 2 MLPE options and both have negative feedback:-
a) For microinverters – reliability issues and problem with warranty
b) For Solar optimizer – communication software issues and problem with warranty
I am therefore confused and hence the question (1) above.
2) What is the warranty period for Tigo Optimizer, Enphase and SolarBridge Microinverters?
Regards
Hello Stephen.
Both Enphase microinverters and a SolarEdge inverter with optimizers will give similar results.
Enphase microinverters have a warranty of 10 years in Australia and 25 years in the US. Solarbridge inverters appear to be similar.
Tigo optimizers have a 25 year warranty.
Another option, other than using microinverters or optimizers is to use solar panels that have panel string optimization. I wrote about one type of this here:
https://www.solarquotes.com.au/blog/maxim-just-killed-microinverter-dc-optimiser/
Hi Ronald,
I have a read about this amazing Maxim Integrated technology. Just wondering whether we can fit this new chip onto a panel with 25 years guarantee (like Sunpower). We can then set and forget about the system and only need to replace the string inverter (located in the garage) after 10 years or so………..no need to worry about costly access to roof. How long is the warranty period for this Maxim chip?
Regards
Hello Stephen.
Maxim says that, while they haven’t been able to field test it for that long, they are confident their technology should last the life of the panels.
Solar panel manufacturers, such as Jinko, give their Maxim panels the same 10 year product warranty and 25 year performance warranty as their other panels. However, Jinko has withdrawn their first generation Maxim panels for causing television reception interference and say the second generation, with this problem fixed, will be available soon.
Hi Ronald,
I have recently had a quote for 38 x 280w Suntech Smart DC panels. I was told that this is the second generation of Maxim panels by SunTech and they have ironed out the tv reception issue, but I am unsure whether this is a market-accepted resolution yet (the installation company is apparently the company involved in testing this second gen product in Australia (SA)). I can’t find any info on it and the quote I was given for the Suntech smart DC panels referred to a Solarquotes article (from 2016 – see https://www.solarquotes.com.au/blog/maxim-just-killed-microinverter-dc-optimiser/) saying how great they were. Given the other installer who gave me a quote said he had not installed any since 2016 and the Solarquotes optimisation article from 2018 suggests that Maxim panels are ‘out of the contest because you just cant get them in Australia’ (see under the heading ‘Which PLO should you choose?’) am I missing something?
Have there been developments regarding these panels and their availability?
I am also concerned about the safety of anything DC. Have seen some horrifying pictures online of the damage a DC arc fault can do. Are my concerns misguided? I am thinking microinverters are my only option but the cost is looking prohibitive at 50% more than the DC panels (or do you ‘only get what you pay for’?)
Thanks,
Louise
Hello Louise
Other manufacturers have cancelled plans to introduce panels using second generation Maxim optimization in Australia because they weren’t able to overcome the interference issues, so its reasonable to be concerned. But, looking on the bright side, the original panels did not always causes problems. It seemed to mostly be a problem where TV or other signal strength was already weak and could be remedied with a new antenna. So hopefully these new panels will be an improvement and won’t be a problem. But I would want to know what they will do if there is a problem. For example, will they replace your TV antenna with a new one? What will they do about poor radio reception if that’s an issue?
In my opinion DC connections that meet Australian standards are safe. So if you get a professional installer who does good quality work you should be fine. But if you want a greater level of safety you can use microinverters. Another option is to use a SolarEdge inverter as they have DC optimizers on every panel which work to prevent a DC arc. (There may be other optimizers that offer similar protection but I am not aware of any.)
Thanks Ronald,
We run our TV through a Foxtel satellite dish so would potential interference be different to a standard TV antenna? The pain of hubby (and eldest son) not being able to get good reception on Fox Sports would more than outweigh the cost of a system which does not have any possibility of reception interference!
Also, will all installers do SolarEdge inverters and what would be the difference in cost to the 38 DC panels (quoted with a Fronius Symo 8.2-3-M inverter for just under $10k)?
I thought getting some quotes would make it easier to choose, but this has meant I am comparing apples and oranges and the more I read about what has been recommended, the more confused I get.
Ultimately, I think I just want safety and reliability, but not at the cost of an arm and a leg.
Thanks!
Louise
I doubt a Foxtel dish would suffer from interference as it is very directional. But I’m not certain of this.
If the roof space where you are planning to put the solar panels doesn’t suffer from a significant amount of shade through the year then there will be little benefit to using either Maxim optimized panels, other optimizers, or microinverters. So if there is no significant shade then don’t worry about getting Maxim optimized panels if you are concerned about interference.
Not all installers use SolarEdge inverters but if you shop around you should be able to find some who do. You are likely to pay a premium over a Fronius inverter but the total cost will depend on the what the installer quotes which can vary.
If you are concerned about safety you can get a usual solar system with a string inverter, such as a Fronius, have it put in by a quality installer and make sure to have it inspected every 5 years to be on the safe side. But if you are willing to pay more for an extra level of safety you can go with a SolarEdge system or microinveters. If you were considering a 38 panel system then one that large will be quite expensive to do with microinverters. I recommend getting a variety of quotes, looking at the prices on offer, and then deciding if you are happy to pay a premium for additional safety.
Thanks Ronald, if Foxtel is unlikely to be affected by interference that’s a bonus, although one installer has asked me if I could move the dish which sounds a bit rich given there are options for this minor shade issue.
Our main shade issue is from a large (think 100 yrs) Norfolk Pine out the front (east side) which would affect morning sun to some degree even with our double storey and reasonably high, primarily north facing pitched roof (we also have a west facing verandah roof).
When asked about Maxim panels, the installer said they would prefer to provide the optimization as part of the panel construction, as done with the Suntech MAXIM modules, as they have one less point of failure per panel. They have apparently done plenty of SolarEdge installs in the past, and weren’t happy with the failure rate of the retro-fit SolarEdge optimizers, and with our place being a high two story job, they don’t want extra failure points to be responsible for. Is this a cop-out to try to get me to go with their SunTech system or is this a legitimate concern?
It seems the more questions I ask, the more confused I get with the answers.
With some morning shade am I correct that optimised panels of some nature or microinverters are my only 2 options?
Thanks heaps.
Louise
If a tree would be shading the panels in the morning I can see why the installer recommended a system with panel optimization. But you can install a system without optimization. In a best case scenario panel optimization will only reduce losses from shade by 25%. So if your system would produce 75% as much energy as an unshaded one, at best optimization will increase that to 81.25% which isn’t a huge improvement. In reality the increase is likely to be much less.
The link Peter T provided does a good job of explaining the problems a number of installers have with SolarEdge inverters.
With regard to relocating a Foxtel dish, my understanding is what Foxtel charges to do it is reasonably low and so — depending on the situation — it may be the best alternative.
Your options are:
1) Install the Maxim optimized panels and have a hopefully small risk there will be interference.
2) Use external optimizers. (Which should not cause interference but this has occurred in some cases.)
3) Install panels without optimization and produce slightly less solar energy but — all else equal — at a lower cost.
4) Use microinverters. For a quite small system microinverters can be reasonably priced but for a large systems they tend to get expensive.
If you want to reduce the chance of a DC arc so it is below its already very low levels then the options I can think of at this time are:
1) Use microinverters.
2) Use a SolarEdge inverter and optimizers. You may have to find an installer who is still happy with SolarEdge to do this.
Louise, the following link and review regarding SolarEdge might provide some clarity on what your installers have said
https://mcelectrical.com.au/blog/solaredge-inverter-optimiser-review/
Hope this helps
We’ve been going through the microinverters vs optimizers thing recently. Our installer said that in harsh SA conditions, microinverters are only warrantied for/ likely to have the same life as new string inverters. Then, either will need replacing. For a string inverter, easy. For microinverters, it means taking every panel off the roof and dealing with each one individually. Guess time will tell if he’s right!
I am just wondering with the passage of time if anyone can shed any further light on this. I am looking at getting solar and was planning on getting micro-inverters but when i just spoke with the installer he was suggesting getting Solar Edge panels with Optimizer to future proof the panels as they would be easier to install batteries on down the track. I have no interest in battery storage at the moment but in time when the technology improves and the cost reduces i am sure it would be something to consider.
He also told me that the optimizers will basically do the same job as the micros and you can monitor each panel and run a Solar Edge HD Wave inverter…….this is all so complicated.
Hi Mark
If you want to get batteries in the future, AC coupling will allow you to install them no matter what type of solar inverter you have. I don’t recommend spending money now to prepare for getting batteries in the future, as battery storage is a rapidly changing field and you risk your current investment going to waste.
That said, both microinverters and SolarEdge’s DC optimisers are effective ways of getting the most out of solar panels. They will both cost more than a simple string inverter though. A cheaper option may be to use panel string optimized solar panels, but they may be hard to find at the moment as Jinko has withdrawn their first generation Maxim optimized panels and their second generation probably won’t be available until next year.
If your roof is unshaded, or has no significant amount of shade through the bulk of the day, then you will only see a small improvement from using microinverters or optimizers or panel string optimized panels. If your roof does suffer from significant shade, then you’ll find it more useful.
Finn’s article is 2+ years old – was wondering if technology has marched in any one direction and that maybe DC optimizers may have moved into pole position.
With the exception of the Enphase dealer, every other salesperson has tried to talk me out of micro inverters with all kinds of concocted horror stories.
I like that with micros we are only dealing with 240VAC. If cost were not an issue, do micros still have the edge today?
If cost were no issue I would say micros have the edge because they eliminate the need for DC cabling on the roof which basically eliminates the chance of a DC arc occurring. This is only an extremely small danger in any system that meets Australian standards, but is an advantage.
Fault detection built into DC optimizers may provide the same level of protection. Normally eliminating something altogether is the best way to avoid problems, but it could be effectively the same. I’d have to look into that.
But where microinverters win, in my opinion, is system resilience. This is because when a string inverter fails the whole system will stop working, but with microinverters if one fails the rest keep functioning. Some people look at this the other way and say that with microinverters there’s more inverters that can fail, so I guess it depends on your personal outlook.
But if price is an issue, then panels with panel string optimization have an edge. They don’t eliminate DC cabling or allow monitoring of individual panels, but have a cost advantage.
I understand Solaredge optimizers provide panel-level monitoring?
That’s correct. Here is SolarEdge’s blurb on it:
https://www.solaredge.com/aus/products/pv-monitoring#/
I was speaking with an installer about DC optimizers vs microinverters. Their recommendation was optimizers for the high output (335W) panels we want to install. Current Enphase microinverters have a maximum input rating of 270W and so presumably the extra 65W the panels can produce at maximum output would be wasted. I did read somewhere that the microinverters may work at higher input wattages, but it wasn’t clear if this would affect the longevity and reliability of the units.
Generally speaking using optimizers will cost you less, especially if the solar system is large or if they are only placed on panels that suffer from shading. But some people like that microinverter systems are more robust as there is no single point of failure. If one microinverter fails the others can keep working.
Hi Mark
Enphase S270 mincroinverters are 260 watts. (You’d think they’d be 270, wouldn’t you?) While panel output 260 watts will mostly be wasted it’s not really a problem as panels very rarely produce their rated output. I wrote about this here:
https://www.solarquotes.com.au/blog/oversizing-solar-arrays/
Generally it makes economic sense to oversize your panel capacity in relation to your inverter capacity whether you are using optimizers or microinverters. Or if you are using neither. While it’s possible that using lower wattage panels would extend the live of microinverters, since you’d be paying more per watt per watt of solar panel capacity it’s only likely to make the economics worse.
Which is best can
just to support what Ronald Brakels wrote, The rated output means that if you have the sun pointed directly orthogonal to your panels’ surface, and the atmosphere is totally clear, the sun is high enough that it is passing through only a small cross section of atmosphere, and the ambient temperatures are relatively low, then your panels could produce at, or close to, their max ratings. Any other conditions and you will see less than rated output.
So the recommendation (whether using optimizers or micro inverters) is to clip the production curve by over sizing the panels relative to the microinverters or optimizers. I have 260 watt panels paired with 225 watt microinverters (15% over size) and my system is one of the highest producing systems (in terms of total kWh per watt of capacity installed) – it routinely ranks in the top 4% in terms of efficiency on PV Output’s website. For a 260 watt microinverter a similar over sizing would suggest a 300 watt panel would work well.
The reason clipping makes sense is that on days that the output is clipped one produces considerably more electricity during the shoulder periods. Also over time panels lose capacity and their is less clipping.
Hi Finn and Ronald,
We are just about to get our panels installed and I noticed that we are getting a small amount of shade (maybe 2-3 panels only in 24) for a few hours in the middle of the day, from a nearby tree.
Do I need to raise this with our installer or just wait to see how much our output is effected and get some optimizers fitted later?
Can I get them fitted to only the few panels that are being shaded and not the rest?
Thanks for all this work boys,
Jason
Hi Jason, Ronald here.
I’d certainly mention the shading to the installer. Just a small amount of shade can greatly reduce the output of a system with a normal string inverter and if its happening in the middle of the day it will take a big chunk out of your system’s output. Generally, it is going to be a lot cheaper to get optimizers fitted from the start then have them put on later. Optimizers can be attached to just the panels that will be shaded but where the shade falls will change with the seasons so that will need to be accounted for. Putting panels on a different part of the roof is also an option. While that may reduce the system’s output it may reduce it by less than shade will.
If it’s your own tree you could just trim it. In Queensland neighbors can be required to trim or remove trees or bushes over 1.5m that shade your property but I believe in other states your right to sunlight isn’t as strong.
Thanks Ronald,
I will get in touch with them tomorrow.
We don’t have any other roof space to use, but looks like this will be a mid winter problem only.
Unfortunately we don’t seem to have such strong laws as in Q, but I will check.
Jason
I have one minor thing to mention about the Robustness section in the article. I experienced firsthand recently that a single microinverter can take down an entire string (AC branch circuit), which was mentioned as a problem only associated with optimizers. If a microinverter has an internal fault that causes the AC branch circuit breaker to trip, the whole string goes down and the fault can be very difficult to pinpoint. In fact, in this case, I thought I was looking for a wiring fault in the trunk cable or home run wiring, when in fact it was a microinverter’s internal failure. If I didn’t hear the pop and see the smoke, I would have wasted a significant amount of time searching for a wiring fault. Granted, this kind of fault is arguably “safer” than a DC fault, but in terms of robustness, this is something to consider or at least be aware of. Most microinverter faults don’t result in this phenomenon where a string goes down, but it can happen.
That said, I still prefer the microinverter system architecture due to the risk of string inverter failure (added potential point of failure) and the mess and cost that is going to cause in terms of replacement in 10, 15, or 20 years. It’s hard enough now finding someone to competently change out or upgrade a transformer-based inverter from 5-10 years ago.
Hi Finn,
Love the website and this article in particular. Really informative to our solar research.
I’m getting quotes at the moment in VIC on a solar system split across my north and west facing roofs.
Talking to the contractors and looking in depth at the minor shading issues we have across our northern roof in the early morning I wanted to get your opinion on whether we should consider DC optimisers considering:
-North and west panels can be connected seperately to the inverter to essentially operate as seperate strip systems into a 5kW frontius inverter
-We can probably fit the panels we need on the northern roof away from any potential shading issues;
-Overall system size we are likely to go with is 4.8kW, but we have the space to make this up to 6.6kW if we choose to invest more.
Considering our situation is it worth considering the capital cost of optimisers for potential, minor shading issues in the AM?
Thanks, Paul
Hi Paul, Ronald here.
Only a very small percentage of a north facing solar system’s output is generated in the first couple of hours after sunrise and optimisers will reduce losses from shade but not eliminate them. So if only your north facing panels are affected by shade early in the morning it may not make economic sense to install optimisers on those that will be affected as they may boost total output by less than 1%.
Let’s say your system produces 8,000 kilowatt-hours a year and spending $400 putting optimisers on the shaded panels will cost you $400 and increase total output by 2%. That will give you an extra 160 kilowatt-hours a year. If that is worth 20 cents a kilowatt-hour it comes to $32. That’s not a bad return on $400 but if you have the option of spending that $400 to get a larger system to begin with that will probably be a better use of the money.
Thanks for the advice Ronald, much appreciated.
Helped me decide that putting optimisers across all panels wasnt worth the capital cost and instead upsized the system a little.
I’ve ended up negotiating with the installer who offered to throw in a few optimisers onto the panels likely to receive minor shading issues. So all in all I think it might be a good outcome.
I have a similar layout with 4.8 kW of panels scattered over North (1.8) and West (3.0) aspects, and also split between an upper and lower storey roof. Shading isn’t an issue but I wonder what difference upper/lower splits might have on performance? The lower storey roof does end up in shade very late in the day almost at sunset but the upper follows about 30 minutes later anyway.
High Tommy
Having panels that are connected to the same Multiple Power Point Tracker (MPPT) on higher and lower roofs shouldn’t affect performance provided they are at the same angle and don’t suffer from shading. As your lower panels are shaded before sunset, unless they have optimizers attached, that will also drag down the performance of the unshaded panels attached to the same MPPT. The good news is, if it is half an hour before sunset you system’s output will be low by then anyway, so you won’t be losing out on much. The bad news is most households self consumption of solar electricity it usually high at this time. You can check what effect shade has on your system by checking the inverter output before and after they are shaded.
Hi Ronald,
I would like to get some advice please regarding panel setup and whether a solaredge optimiser will likely increase the yield compared to fronius.
I plan to put on a 6.6kW system on my roof. Roughly half half split between West and NorthWest roofs. The west roof will be on tilt frames as its flat. The NW roof has roughly a 15 degree pitch. As the main house has a flat corrugated roof, birds tend to walk and maybe poo around on the roof as I could hear them from my house. In this instance, is it better to put solaredge on each panel (due to bird poo droppings and hence potential shading?) Or fronius is fine? Solaredge allows me to monitor each panel individually so if there is poo, I would be able to tell due to lower solar generation?
I do not have any other shading from trees or neighbour’s house. Only concern is with the bird poo.
Thanks
If you look at your roof and you can see bird droppings there now it indicates they are also likely to build up on your solar panels. If there are no droppings then the bird poo problem may not be too bad or it might have rained recently.
Your options are:
1) Just use the Fronius inverter and solar panels and take no precautions. Presumably you will lose some output due to bird poo but you will save money on the installation and this may make it worthwhile.
2) Use panel optimizers without panel level monitoring. If one panel gets pooed on it will reduce the output of that panel but it won’t bring down the output of other panels. (Panels with Maxim built in optimization can also be used if available — but note in the past they have caused caused interference with TV reception.)
3) Use microinverters. These allow each panel to operate independently, but tend to be expensive. Especially for a 6.6 kilowatt system.
4) Use SolarEdge with panel level monitoring, or you can look for a different system that also provides it, although I can’t think of one off the top of my head. This has the advantage of letting you know if one panel is performing poorly. But decide if you need panel level monitoring. If you see one panel has probably been pooed on will you make the effort to get it cleaned or will you just wait for it to rain? If it’s the latter then knowing that a particular panel has been pooed on isn’t that useful.
5) Buy a cat.
Number one is the cheapest option. (Between vet bills and food cats can be expensive.) The lower cost means most people would probably consider it cost effective, but it all depends on how bad the poo problem is and how much you are willing to spend to get the most power out of your system. If money is no limit then Sunpower X or E series panels with optimizers are probably the most poo resistant panels of all.
Hi Finn,
Is there any difference with buying a panel with optimiser built in vs attaching one later? Any particular brands do this well ?
Hi Jake, Ronald here.
You can just go with whatever is most cost effective. There should be no difference in performance though it’s possible to make a good argument that factory installed optimizers should be more reliable as the factory can perfect the process and potentially completely automate it to eliminate direct human error. But really it’s the warranties and how reliable the installer is that is important for a household. The trend is for more optimizers to be factory installed but after factory installations won’t disappear any time soon as people may want just one or two panels to have optimizers to handle a shade issue.
Hi Ron,
I am considering microinverters as I don’t have enough roof space for a reasonable installation of 5kw without placing some panels on the east, north and west facing areas. I live in Central Queensland where we don’t have regular poo washing rain but many days of quite hot temperatures and wondered how this would effect the electronics of the inverters? Electrolytic capacitors for instance We don’t have frost though. Kind regards Don.
Hi Don, this is Ron
Heat doesn’t do electronics any good, but the only microinverters you can get these days are pretty tough. While it gets very hot under a solar panel, microinverter’s small size helps them dissipate the heat they generate themselves. All else equal I would expect microinverters to have a shorter lifespan in a hot environment than a cool one, but you still get the same warranty no matter where you are in Australia. Enphase microinverters have a 10 year year warranty here and it is 25 years in the US.
Dairy Farmer. Looking at installation of a 100kw system. On a machinery shed roof. No shade cover on roof.
Quote 1. solaredge inverter with p700 power optimizers. Jinko 330 watt solar panels. 302 panels (original quote was for mono brand panels)
Quote 2. Fronious or ABB inverter. Jinko 315 watt panels. 316 panels
Are the power inverters worth it on this size system. We can have regular power outages with storms in our area. They supposedly help with protection and early shutdown? Location South West Victoria. Will the power inverters help in overcast days that we have?
Hi Kevin
If there is no shade, having optimizers on the panels with the SolarEdge inverter won’t result in a large increase in output. Maybe only a couple of percent. (But note if you use a SolarEdge inverter the panels will have to have solar edge optimizers.) SolarEdge has a good warranty, but unless you get a great deal on it is likely to be more cost effective to use a different inverter.
Fronius inverters have a great reputation for reliability but are more expensive than ABB.
Jinko are a lower cost but still reliable panel. I believe all Jinko panels are ammonia corrosion resistant, but I would still check with the installer just in case. This is important if livestock are near the building as their urine will release ammonia.
I would say neither. And ABB just quit the inverter business, so if they are offering it, it is a closeout special and highly not recommended. And Fronius has an awful reputation for reliability. I replaced their old IG series inverters routinely.
As for the SolarEdge, if you are going the MLPE route I recommend microinverters since you will undoubtedly need to replace an optimizers’ inverter once or twice in a 25-year span and microinverters are warranted for that whole term. You won’t gain much power with MLPE in this scenario probably, but you will gain a whole lot of warranty and much much better monitoring capability (which is really the only way to hold module manufacturers to their power warranty in a reasonably cost-effective manner). If you are going to go with a string inverter, choose another brand. SMA would be a good choice, but you should still budget for a replacement at least once. That is something that dealers rarely build into their financial comparison of MLPE vs string inverters.
There is a case to be made for MLPE at almost any system rating (other than utility-scale perhaps). It all depends on what’s important to you. Risk, safety, maintenance, and other factors play into residential and commercial solar energy decisions.
Note: If you are not in the US, the microinverter warranties may vary.
10 years for Enphase here
That’s too bad. At least they have the confidence to offer 25 years in the US with the Same product. Maybe it’s a competition or legal thing….
Thanks guys. The 2 quotes are $10,000 apart. the solaregde system with Power Optimizers being the dearer. There workings out show they should save us an extra $2500 a year over the other company system. So for 302 power optimizers for a extra $10000 seam a good deal. if they can save an extra $2500 a year. seams a simple choice for the 25 years the system should last?????
And the solaredge are back to using JA Panels as well
Hi Kevin
With 302 optimisers the solar system you are looking at might be around 90 kilowatts. With that large a system the SolarEdge system with its optimisers may be able to save you $2,500 a year. If the installation doesn’t suffer form any shading I would expect the savings to be much less than this, but even if it is one-third what they say you may consider it a good return when SolarEdge’s well above average 12 year warranty is taken into account.
So are the JA panels a good quality enough panel. They’d be 330w panels to get the 99.66kw. the Jinko panels were 315w for 316 panels. I’ve been told by a sparky that both brands are Chinese rubbish and Q cell are better. Sent all panels made in China now??
In our Solar 101 Guide we have a graphic showing all the panels we recommend and consider to be reliable and well supported:
https://www.solarquotes.com.au/solar101.html
JA Solar, Jinko, and QCELLS are all on it. JA and Jinko are lower cost panels but still reliable and you are unlikely to have problems. QCELLS is generally considered to be a better quality panel but costs more. Jinko panels have a 10 year product warranty while JA Solar and QCELLS have 12 year product warranties. You can compare them using the table here:
https://www.solarquotes.com.au/panels/comparison/compare-solar-panels/
G’day Kevin,
Given the outages you have mentioned, then I would recommend that you seriously consider the Enphase solution, specifically the new Enphase Ensemble platform, as this should provide you with a system that will continue to operate seamlessly when the grid goes down.
For further info, then please check out the promo video here:
https://youtu.be/-zm0NMKW7k4
Finally, and after checking with your accountant, then you might be able to purchase the microinverters as a separate item using a separate purchase order and then write that part of your system off using the ‘instant asset tax write-off’, providing of course, that the price of the micros are below the threshold level. The incentive was increased to $30K leading up to 30 June, but it may have reverted back to $25K now.
Hope this helps …
So I am just asking can I use micro AC panels just for my hot water system
Just add my hot water is 30% of my power bill can I use micro AC panels just for this its a 1.3KW system heat pump and to add when I do get batteries for my solar panels can I change all my light bulbs to 12volt because I would run a cable from the batteries to the light circuits as I only have light on it no fans etc????
HI, We have a north facing roof but get shade on one side until 830am and then the other side starts to get shaded by 315pm. Not sure how winter sun will fall on the roof yet either (should I wait??). I have had been given 2 options so far that are similar price. – a 6.6kw Fronius with 5 optimisers or 8.6kw Sungrow with no optimisers. I am also waiting for the price of an Enphase system. Thanks!
Hello Lisa
It sounds to me that you’d be better off putting a system on the side that is shaded until 8:30 in the morning. Because a north facing solar system will produce most of its output in the middle of the day you will loose very little generation in total from the shading. Not having shade afternoon will also be good if you use a lot of air conditioning in summer.
You can have an installer use a suneye device that will determine exactly how much shade your roof will have through the year:
https://www.solarquotes.com.au/blog/how-to-be-sure-that-shading-wont-kill-your-solar-power-systems-output/
Alternatively, you could look at how close the shadows in the afternoon get to your roof in the afternoon and then work out where they are likely to fall in winter, but if you don’t have any experience with this it will be difficult to do.
A Fronius is considered a better inverter than a Sungrow and those 5 optimisers should reduce the losses from shade, but the Sungrow system is 30% larger, so even if it suffers considerably more losses from shade, it could end up producing considerably more output in total.
We already have a 1.5kw system. We want to upgrade but we do have limited space on our roof. It has been suggested we remove the old ones and put up microinverters because of roofline. Unsure of what to do.
The first thing I’ll mention is if you have an old high solar feed-in tariff for your old system you are likely to lose that if you make any major changes. If you do have an old high feed-in tariff you’ll need to decide if it is worth losing it.
If you get rid of your old system it will let you fit more modern, higher efficiency panels on your roof and generate more solar electricity overall than if you left it there. You will also have the benefit of having a completely new system with a new set of warranties. While your old system may have many years of life left, it could be on its last legs if its hardware isn’t good quality or it wasn’t installed well.
Because larger solar systems generally cost less per watt, the cost of removing the old solar system may be covered by the savings from getting a larger system.
Microinverters are a very flexible and effective way to install solar. But that comes at the expensive of greater expense. I recommend getting a few quotes from reputable installers and seeing what they offer you.
I don’t get the modern thinking about solar power. The traditional way of connecting solar panels is in parallel, not a series string, so the voltage is kept low and you just use heavy duty leads to cope with the amps. Arcing may be a potential problem but after 20 years or so running this system I haven’t had a problem and I did the installation myself. No complex electronics on the roof to break down, and ok so my Australian made inverter probably doesn’t meet the current standards because it was second hand when I bought and so would be about 30 years old, and still going strong.
Please don’t confuse the punters with terms like AC panels. The panels are still DC, and there is no way of making an AC panel, it is the micro inverter that is changing the current from DC too AC, but the panel is and always will be DC.
I also had a grid connected system installed on another property and it produced more power than the house used but I had to pay the electrical company $1/day for giving them electricity. Grid connection a good thing to avoid since when the grid goes down a simple grid connected system with no battery storage will go down with it and so will all your communications devices because these days they all rely on grid power. Australian once had the best communication system in the world, with it’s own power system backed up by batteries, so even when the grid went down you could ring emergency services, but now that highly reliable system is being closed down because privatised Telecom and power companies can make more money selling us stuff we don’t need.
With a very low Sunspot activity period we are now entering,there is an increased likelihood of a big solar flare or Mass Coronal Ejection(MCE) hitting earth and taking the grid out. Last time we had one of these hit the planet we only had very basic wire services and the operators got a shock. Whether Solar Panels will survive an MCE is an interesting point, inverters probably won’t so it could be back to basic living with candles. Good luck with the micro inverters on the roof.
Wading in with my own potentially very dumb questions…
I’m unclear on what a Solar Optimizer actually is and how it works. Certainly my solar installer couldn’t tell me. So I “did my own research”…
From what I could/can glean from where I looked on the internet, a DC power optimizer is actually a DC to DC converter of some sort. And I’m guessing (but don’t know) that the panel’s voltage is regulated so that it’s output achieves the same current throughput as the rest of the panels in the chain, so as not to throttle them when the panel is shaded.
Question 1 – Am I way off track here? And if I am way of track – then what are they and how do they really work?
Last time I looked, the only ways to convert DC to DC were by transforming to AC using a chopper switch, a transformer and a bridge rectifier, or using a single inductor/chopper as used in DC:DC booster circuits. So my second question is:
Question 2 – Aren’t the losses in the DC to DC conversion process equivalent to those of a micro inverter, and converting a micro inverter’s output back to DC to charge a battery?
I would have thought they would have been higher if anything, which begs the question do they offer any advantages in terms of efficiency where I’m planning to use a battery?
All answers greatly appreciated…
Hi Gabriel, Ronald here.
Solar panel optimizers are DC to DC converters and they work to maximize the amount of energy the panel it’s attached to can supply the solar inverter. But these days solid state electronics can directly alter DC voltages without inverting it to AC power first. They can be up to 98% efficient, but their modest power losses mean there may be little or no benefit where shading is minor. A Danish study I wrote about came to this conclusion:
https://www.solarquotes.com.au/blog/panel-optimisers-danish-study/
One important point is many manufacturers will not warrant their solar panels if they are installed in shaded areas without optimizers.
I looked it up about 4 years ago, so I’m incredibly rusty, but…
The problem is that when a panel gets shaded, the voltage of that panel drops to zero. Panels in parallel average the voltage across them, so if you (say) have one out of 5 panels with zero voltage, the remaining 4 can only produce at 4/5th = 80% i.e. you get a 20% drop across the other panels, too. (Still better than the serial installation!)
Micro-inverters fix this by each panel converting DC to AC, then the AC gets combined, so one panel being shaded only drops out that panel.
Optimizers are basically bypass diodes that allow the panel to be bypassed, so the other panels keep working at 100% voltage. The DC gets combined and converted into AC at the inverter. Hence the overall result whether using micro-inverters or optimizers is the same.
IIRC, panels can be constructed as several internal electrical ‘units’, each having a bypass diode, so if you have part-shading, the rest of the panel can keep working. These would be internally-optimized. I’m not sure if this happened; like I said, I was looking into it some years ago.
Hi
I note this article was written in 2015 and last updated in 2018. Has your thinking changed at all on optimizers v micro-inverters?
Optimizers and microinverters have their individual pros and cons which haven’t really changed since the article was first written. I’d just recommend considering if a string inverter without optimized panels will meet your needs at a lower cost.
Thank you for finally doing a real in-depth comparison instead of just copy/pasta the same superficial stuff that is everywhere else. As someone that wants to gain real honest truthful comparisons to do their own design, this kind of article is most valuable. FWIW I am planning to make an off grid RV that can plug into my home based system while maximizing my tax credit for the home install portion. i need the detail on ALL of the components and this article proved excellent and contains subjective as well as objective analysis that I need to help me with this design.
Hi there and thanks so much for writing this article. I am rather green when it comes to solar and so understanding the 3 different systems is helpful. That being said we are currently looking at installing solar on our home and I’m still trying to sift through everything. The origional roof is east and west facing while our new roof (renovation) will be large but south facing. So far most have quoted on a 6.6kw system with 15 panels on the east and west side and either in string or one with DC optimiser. I have also received a different quote for a 10kw system with 21 panels which I can only assume is string as its not clear and also with panels on the south facing roof which I also dont quite follow. I know in the early stages of this article it spoke to battery integration etc, while we are not looking to have battery storage now, its a possibility down the line. I was told the DC optimised system was a good mid-point between string and mico-inverter but there is obviously quite a bit more to it.
Is there still benefit to string as I know its cheaper but there is the risk of lower efficiency due to shade spots etc? One later comment mentioned installing a portion in string with some using an optimiser or micro inverter, how does this work?
Any guidance from anyone in the know would be greatly appreciated.
Hi Pierre,
South facing roof isn’t as silly as it might sound initially. The only solar panel that doesn’t help you out is the one you haven’t installed.
https://www.solarquotes.com.au/blog/roof-orientation-solar-australia/
Microinverters are certainly most flexible but not as readily oversized compared to say a Sungrow with 200% overdrive available if you do go for a battery.
Fronius string inverters also have a great deal of flexibility because thy will handle parallel string designs while maintaining excellent efficiency because of a great MPPT program and fan cooling.
The inherent nature of split cell panels now means micros don’t have the advantage they once did in terms of shade tolerance, however optimisers can offer some further design flexibility and in some cases offer individual panel level monitoring, however that seems to me to be a feature people are mad keen to buy and soon forget about.
Hi there Anthony and many thanks for your reply.
I read your article on roof orientation etc (well written and researched). Again, I am rather green and so from my initial read it would seem to be better to have any panels rather than none, even if a vast amount of them will be south facing?
Most proposals that have been sent my way revolve around a 6.6kw system with 5kw inverter and simple string array. The panels being mounted on the east and west roof line. As per your article, the west facing side will actually continue to produce for many hours especially after 3pm when rates tend to increase.
I have received a quote for a 10.56kw system with 10kw inverter that is 24 panels and mounted on all the roof spaces. This does seem like a good way to “future proof” by maximising the panel usage but I again am wondering if the string array is the best for long term or whether one needs to make that extra investment into the micro inverter or optimser however you point out that they dont have the same hold that the used to.
What would be the best way for me as a pretty regular Joe to understand exactly what im getting into and best way forward? Whenever i receive a quote there are a fair amount of technical specs which most wouldnt understand and it makes it difficult for one to know whether apples are being compared with apples or whether a flying fish has been chucked into the mix.
Your help is greatly appreciated.
Hi Pierre,
We can do a comparison if you email us some documents but more generally you can have a fiddle with https://pvwatts.nrel.gov/ to work out what panels will yield, facing wherever you program the simulator.
Beware that Enphase needs a savvy designer to make it work at peak efficiency. Getting the full 133% overdrive allowed under Australian rules can be tricky in terms of panel choice. String systems generally have more leeway because you’re dealing with multiple panels and wider voltage windows.
Thanks Anthony. Happy to email some details/plans through if helpful – please let me know best email address.
Much appreciated
Check your inbox Pierre 😉