Maxim panels are gaining traction in Australia as a superior solution for optimising solar panels in shaded conditions. But does Maxim really work?  In a previous blog, I explained why I thought Maxim was the closest thing to shade proof solar, but at that point, I had not performed any testing myself.  It’s been six months since we installed our first Maxim integrated panels and around five months since I started running comparative testing of Maxim on my warehouse roof. This post will reveal the results of my testing and the complications I had along the way.

The comparison was always going to be with the optimiser incumbent, SolarEdge. The inverter to match with Maxim optimisers was a no-brainer: Fronius. The question has been asked: “why can’t we match Maxim integrated panels with external SolarEdge optimisers.”
You just can’t.

The comparative test, that was meant to take a week or two,  turned into a six-month learning curve, some of which I’ll share in this post.

Let me be clear of my bias. SolarEdge is a great inverter; Fronius is the best. I don’t think that deserves an apology or even an explanation but in a breath:

The Fronius Smart Meter, load control, Solar.Web, reliability, in-built DC isolator, Austrian built. Check-mate.


The original test was set up as follows:

So when I had the systems running over the Christmas break and SolarEdge was continually outperforming Fronius Maxim, I was in denial. The Maxim/Fronius system was running about five percent worse in unshaded conditions and only equal to SolarEge when individual cell strings were shaded. So although Maxim was not affected so badly by shade, something was happening to make Maxim panels run worse than SolarEdge in non-shaded conditions. “Maxim is a farce,” I thought.

I tested and retested. I checked the panel flash-test data. It was comparable. I spoke regularly with SolarEdge, Fronius, Maxim and Jinko to try to nut out the problem. All showed a vested interest in my testing and spent time with me trying to make sense of my results. I switched my whole current kWh meters around, adjusted DC cable lengths and ensured both inverters were on the same AC voltage reference. One day in frustration I disconnected and reconnected the SolarEdge inverter under load. Don’t try that at home. The inverter let the smoke out and I didn’t catch it. Aaaaargh!  It was after this I wrote a curt email to my new “friends” at Maxim an email advising them we were no longer friends and I wanted a refund.

“Maxim is a farce,” I thought.

The next day I thought again and set up the third test on my warehouse roof -as a control:


With all 3 systems running together, I discovered my new Canadian/Fronius panels were running equal to the Maxim/Fronius but still five percent worse than SolarEdge system.

I then added external SolarEdge optimizers to the standard Canadian panels and switched them over to my SolarEdge inverter. Waddayaknow, they were running five percent better than Fronius/Maxim. It was clearly not the fault of Maxim. Either SolarEdge was boosting the performance of the panels, or Fronius was hindering. Either way, it was not looking good for Fronius. I called SolarEdge who claimed that, at most, I would see a one percent increase in unshaded conditions due to mismatch. However, with new, clean, unshaded panels, SolarEdge probably wasn’t boosting the performance of the panels at all. By process of elimination, I had to blame Fronius.

Maxim’s input

I arranged a tele-conference with Maxim in China and in the USA. Daniel from Maxim honed in on the apparent problem. I only have a string of 8 panels on the Fronius 5kW inverter. My string voltage was dropping below the Fronius MPPT optimal range with the high summer temperatures. I pulled out the spec and at went downstairs to read the actual reading of the inverter. “You idiot,” I said out loud to myself. But at least I knew how to solve the problem. I knew the voltage had to be over 240 volts to get the best performance out of the inverter, but surely being a tad under 240v wasn’t going to affect the efficiency by five percent?! If this is the case, then Fronius has some serious design restrictions and SolarEdge may have won the contest!

Is Fronius to blame?

I called Rod from Fronius.

“Mr Maxim, what’s happenin’,”

answered Rod. He’s always happy that bloke. I should get a job with Fronius, then I’d be happy too.

“Rod, I think I’ve found the problem. If my string voltage is under 240 volts DC, how much power do you think I will lose? Five percent?”

Ah really M.C? Nah, that doesn’t add up. You’re not going to get a five percent loss because you’re just under our optimal MPPT voltage range. Hey, one of our Engineers will be over from Fronius in Austria in a few weeks and we’re coming up to Brisbane. We’ll drop into your office and see if we can’t work it out. Have you met Keisha?


A visit from Fronius.

Rod, Marcus, Hans and Keisha came for a meeting in the end of March. Keshia Noronho became the Managing Director of Fronius Australia in January 2017 when her brother Adrian Noronho took up his new role in Fronius International. Adrian is a top bloke. It’s obvious that the success of Fronius in Australia – and the positivity and intelligence that Fronius Australia oozes – is owed to Adrian’s leadership. After meeting his sister Keisha briefly, I get the impression that Fronius is in safe hands.

We talked about the Fronius roadmap and the future of batteries. But I was keen to get one thing sorted. What was wrong with my Fronius/ Maxim system?! If we are losing five percent in performance because we are under the optimal MPPT voltage, then Fronius has some serious design restrictions.

Rod came prepared. “We have a power ratio problem,” said Rod. We looked over the Fronius efficiency data charts. The reason my system was underperforming was simply because I was running 2.12kW of panels on a 5kW inverter. The inverter runs better with higher power input.

Facepalm.We never sell the True Value Solar style “2kw of panels with a huge upgradable 5kw inverter”. However, I had naively figured that because I ran both inverters with the same setup, any insignificant losses would occur on both Fronius and SolarEdge. Seems I was wrong. There were a couple of ways to test, but the quickest was to throw another 8 panels on each system.


A Maxim retest

I redesigned the systems with 16 panels on each string. This increased the voltage and the power in both systems.


It worked. Who’d a thunk? Finally, Fronius/Maxim was performing about as well as SolarEdge in unshaded conditions. Fronius seemed to work worse in low light conditions when the power was sitting below 1000 watts, but better in the middle of the day with full power. Over a 7 day period, SolarEdge and Maxim / Fronius were performing almost identically.

Remember I only installed 4.2kW of panels, so if our common 6.5kW were installed on each system, Fronius may have marginally outperformed. But we are splitting hairs.


Fronius/Maxim VS SolarEdge shade test

After four months of testing, I could finally perform my comparative shade test.

I performed different shade tests over a number of weeks trying to gauge the difference in production between Maxim and SolarEdge. The test was made by shading multiple cells on both systems and reading the results after about 24 hours. It’s hard to know how to quantify the increase in performance, so I have broken it down to it’s simplest form.

For every cell that was shaded (in one cell string only), Maxim ran  0.3% to 0.4% better than solarEdge.

This test was relatively consistent if I shaded 4 cells or 40 cells on the one cell string and in multiple panels across both systems.

To try and put an actual value on this any given roof would be like counting hairs on your head.

  • First, my test used fly screen for consistency of shading. How accurately represents shading compared to tree shading is yet unknown.
  • Second, try counting how many cells you would have shaded in a non-uniform manner across your panels, across different times of the day, and different months of the year.

The point is that I have proven the claim. A Maxim/ Fronius system (designed correctly) will give higher output in scattered shade conditions than SolarEdge. With 32 cells shaded, I measured that maxim had an increase in performance of more than 10 percent over a 3 day period.

With 32 cells shaded, I measured that maxim had an increase in performance of more than 10 percent over a 3 day period.

Field experience

To date, we have installed 27 systems with Maxim panels. (There was a nervous period earlier on where we stopped selling them until I could confirm they were working). As subjective as this next statement is, Fronius Solar.Web data shows me Maxim is producing well in the various homes we have used them with. Our electricians have also commented on how surprised Maxim is working in scattered shade.

On the downside, out of the 27 systems installed, we have had 7 that have caused issues with TV reception. In every case, it has been in a home where the TV antenna was right on the edge of having bad reception, and Maxim interference pushed it over the edge. To fix these jobs we have just replaced the antenna, but we are looking into getting a filter that will resolve the problem more easily. We’ve also had TV interference issues with SolarEdge and Enphase in the past, though it seems SolarEdge have fixed that issue with their most recent optimisers.

My next test: The new SolarEdge HD Wave

While I’m still a fan of Fronius, I’ve gained further insight into the benefit of SolarEdge. Most notably was that SolarEdge was performing better in early mornings and late afternoons. (Comparing the performance charts of both Fronius and SolarEdge have confirmed my tests). SolarEdge is about to release a new HD Wave inverter, which used a new technology with a higher efficiency. SolarEdge is also releasing products which will compete with Fronius’s load control. Gavin from SolarEdge has generously loaned me one of the only two HD wave inverters in the country to test. In my next test, I’ll compare a 3kW solarEdge HD Wave with a 3kW Fronius Primo.

But I feel that I now have a test that gives me an answer to the question I was originally asking – “SolarEdge or Maxim?”

For me, the answer remains as Maxim.

If the question was “SolarEdge HD Wave or Fronius?” Stay tuned.

Mark Cavanagh


14 Comments on Maxim solar panel optimisers vs SolarEdge – Test results

Mark C said : administrator Report 3 weeks ago

Hi Kye, Interesting to hear that you have had such a bad experience with reception issues. If you have little to no shade, I wouldn't be too worried about using optimizers at all. I guess the external optimizers they are offering are Tigo? If you have shade on just a few panels, then you could ask them for 290W Jinko and maybe just a few Tigo optimisers "selectively deployed" on shaded panels.

kye topping said : Guest Report 3 weeks ago

hi Mark, very interesting read. I recently had a 5kw fronius inverter installed along with 24 jinko maxim panels, now it works beautifully the problem is it interferes with my neighbours TV reception. my solar installer have been great and tried to replace his antenna but that did not work nor did relocating it due to the proximity and direction. so as a short term fix they supplied him with a digital satellite receiver however this is not a long term solution as technically i am still in breach of the radio communications act which i discovered when my neighbour reported the interference to ACMA. my solar installer has now given me 2 options, option 1 replace all the panels with standard jinko 270w panels and install external optimisers. option 2 replace all panels with standard jinko 290w panels but no optimisers which will up my solar performance by approx 0.6Kw. obviously i realise I'm restricted to 5kw with the inverter but it doesn't hurt to have the ability to produce more than can be used. my question is what would be the best option to pick, my roof gets little to no shade other than clouds as my property is quite raised compared to surrounding properties however I'm curious if i choose not to go with optimisers will this effect any ability with battery storage or future upgrades? would certainly appreciate your advice thanks

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Mark C said : administrator Report 3 months ago

Hi Alan, Thanks for your comments. You raise a good point. The answer is simple, but I probably didn't explain it clearly. I used a third set of panels as a control. The third set was just plain Canadian 265. When I put on external SolarEdge optimisers, they performed like the SolarEdge system. When I put them straight on the Fronius inverter (no shade), (i had 2 Fronius inverters running) They performed identically to the Maxim panels on a Fronius inverter. Shame i didnt use Solar Analytics to record it, but the results were really clear. Both inverter data sheets on power/voltage/efficiency ratios were in line with my results -which was really affirming. Does this answer your concern?

Alan said : Guest Report 3 months ago

Mark I'm in Melbourne and looking to buy a 4KW PV system. I'm not a Solar aficionado but I am interested in optimisation. I expect, (probably) like you that imbedding MPPT functionality or more within the panel - even at the cell level is the way of the future. That said I was surprised by the design of your test. Whilst you gush effusively about the result vindicating Maxim - it wasn't clear to me that that was so. Obviously you were never able to control the testing to just test Maxim against Solar Edge Optimisers - the panels were always different. Presumably this design weakness will always be so when performing field tests even if the panels were from the same manufacturer. Nevertheless you make claims about the relative low light or shading abilities of both optimiser approaches? Why mightn't the characteristics of the respective panels have had an influence on the result? Why are you able to assert that differences are down to the inverters? As a "leading light" in the industry I expected more rigour - or is the fault mine - a lack of understanding of the science behind PV? The battle between Solar Edge and Enphase shows the price sensitivity of the solar industry. Solar Edge GM 34% and Enphase 13% (Q1/17). Enphase is (still) loosing money. You trumpet "With 32 cells shaded, I measured that maxim had an increase in performance of more than 10 percent over a 3 day period". Even if that was so, and you provide no substantive corroberation, if there is a price premium will the market pay it? Presumably Enphase is in the difficult financial position they are in, not because of the competition with Maxim (yet) but Soar Edge. Obviously they have had to cut margins to compete on price with SE. It wouldn't surprise me to see that Maxim have to do the same thing. Maybe the outcome will be different - too early to tell. Regards Alan

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Mark Cavanagh said : administrator Report 3 months ago

Hi Mark, I just had a look at your roof line. You don't need panel optimisation because you don't seem to have shade. REC panels are a better panel than the Jinko panels that have embedded Maxim optimesers. Because REC panels don't have "Module level power electronics" it will not interfere with your TV reception at all. Stick with REC for your place!

Mark Cavanagh said : administrator Report 3 months ago

Hi Peter, Thanks! Yeh, that's correct (you can get that detail on most standard panel specs). But it is also to do with the inverter. Inverters have a power ratio efficiency curves, so a 5kW inverter runs less efficiently with only 1kW on it. Fronius runs a bit worse than solarEdge early mornings.

Mark Cavanagh said : administrator Report 3 months ago

Thanks, Craig! If only! Maxim with Twin Peaks, that would be the best! Maxim is inbuilt to the panels, and as far as I know only Jinko and Trina currently offer Maxim. I've asked REC, and it seems it's not in their plan. But ask them! The more that ask, the better chance we've got of them acting! Mark

Craig said : Guest Report 3 months ago

Hey Mark. Great write up mate. In the comments you say we can use REC or Sunpower panels with the Fronius inverter. Can you can a REC panels with Maxim optimisers?

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Peter T said : Guest Report 3 months ago

G'day Mark. Thanks for another great article mate. In regards to early morning and late evening performance, I must say that I was under the impression that this was more a factor of the panels themselves than any specific inverter. Is my understanding incorrect here?

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Mark Blayney said : Guest Report 3 months ago

Very interesting read thanks Mark. It has made me wonder how the system I am getting from you would compare in relation to that test ~ 24x275w REC Twin Peak panels + Fronius Primo 5 ? And we get sometimes flakey TV reception where we are at Caboolture so will this system affect the signal negatively, as in will we need some sort of filter or extra signal booster ?

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Mark C said : administrator Report 3 months ago

No Problem Andrew. Glad we got the result we were looking for. I was just briefing Steve our electrician on your job. Should be a great one for Maxim! Mark Cavanagh

Mark C said : administrator Report 3 months ago

Hi, Mark. I'm Still not so sure about SolarEdge. So many benefits of Fronius. First, I'd AC couple Tesla rather than go to DC coupling an LG. Affordable load control for hot water, and it just seems like a better build (Australia vs China). Next, we can use REC or Sunpower panels without the massive added cost of external optimisers. I'm just testing the new SolarEdge HD Wave and I must admit low light (or low power) is a factor to consider. Mark Cavanagh

Mark Stevens said : Guest Report 4 months ago

If the question is “SolarEdge or Maxim?”, it sounds like the answer is: Maxim if there's partial shading SolarEdge if there's no shading, as you gain the benefits of better low-light performance, panel-level monitoring, 'Safe DC', a longer warranty and the option of DC Coupled battery storage

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Andrew said : Guest Report 4 months ago

Thank for the writeup, Mark, just in time for the 50 Maxim panels you're installing for us next week!

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