Power Optimisers - What are they? And do you really need them?

I knew nothing about optimizers before this video. Thanks for an excellent and straightforward explanation!

This is the best explanation I've found so far, well done!

* NOTES SINCE PUBLICATION * At 6:34 I over-simplified how the optimiser manages the current. In reality, the inverter first maximises the power from the panel by adjusting the voltage via MPPT, then performs a DC-DC conversion, decreasing the voltage to bring the current in line with the rest of the string. At 7:45, Actually, one or more of the bypass diodes will only kick in if there is a difference in shading across that particular panel. If there is shading across the whole of the panel (as in the diagram) the optimiser should still be able to manage that. And at 14:17 my maths is clearly rubbish - the total production with 12 x 300W panels would of course be 3.6kW, not 4.8kW!

We replace on average about 2 x Solar Edge optimisers per year, some on our own installations, some on other peoples. We install about 50 domestic projects per year. We can't really compare this rate to either Tigo optimisers or Enphase micro-inverters as we don't install them. The good thing is that the faulty optimiser can be pinpointed so we don't have to remove half of the array to locate the problem. For the client, Solar Edge will cover the cost of labour and some of the scaffolding costs. For most replacements we can use an aluminium access tower to get up to the roof and locate the fault. The cost of this is easily covered by the Solar Edge warranty. However, the jobs that tend to require a full scaffold are where we need to span over above conservatories or where there is a pitched roof on a lower storey beneath the roof with the panels. For these replacements the client typically does end up having to cover some of the scaffold costs. The more difficult the roof is to access, the more costly it'll be to deal with faults which would need to be factored into any potential client's decision making. There is an argument to install optimisers & microinverters in the loft space beneath the panels. This would make replacement much easier and less costly. We don't do this as it would mean making a cable penetration through the roof beneath every panel. It would also means installing jumper cables between each panel and it's corresponding optimiser for both the +ve and -ve cables meaning more connections in total. Some attics are converted, so for these it's a non-starter to do this and the optimisers have to go on the roof.

Another very informative video. Many thanks for all your effort that goes into them - as a relative non-expert I find them excellent at helping improve my knowledge and they always provide food for thought.

Another superbly clear and informative video! Thank you.

Thank you for your interesting presentation. I have a 14 panel system with a Solar Edge inverter and optimisers on each panel which was installed in 2017. In 2021 one of the optimisers failed but caused the entire system to shut down. The optimiser was replaced, at a considerable cost, but just over a year later another one failed, again causing the entire system to shut down. It was replaced again at a considerable cost to me. a couple of months ago a third optimiser failed but I only lost output from the associated panel, until a few days ago when the entire output was lost. The inverter is still functioning and recording a fault on one panel which would suggest that the optimiser has failed completely. Solar Edge has provided replacement optimisers under their "limited product warranty" but they have not offered to provide any support for the labour cost or scaffolding. It does suggest that the undisclosed failure rate of the optimisers is somewhat higher than the advertised reliability.

My son & I have very similar solar systems installed by the same supplier. We both have JA Solar 395W panels (he has 12, I have 8) & both arrays face West. Neither of the arrays have shading issues. However I have 4 optimisers & he has none. Why the difference? Well I think we both went with what the supplier recommended. In theory, all things being equal, the ratio of my solar output to his should be 0.666 (8/12) & right now, in Summer, it is. However in the period October to January it consistently ranged from 0.71 to 0.735. It was like I had 8½ panels to his 12. I put this down to my four optimisers. That said, given solar generation in winter is pathetically low, the value of the 'extra' is worth two tenths of bugger all! Had I had my time again, I would NOT have had optimisers put in & saved a few hundred quid.

Gosh another excellent video, well thought out, presented and most articulate. Great work. Ty Gary!

We had a discussion with our installer about Solaredge Optimiser reliability. They were replacing 10 a year over the 20,000 panels they had deployed, so a 0.05% chance of failure per panel per year. Thought I'd mention here since the data for this doesn't seem to be overly available.

Thanks for your video's, Gary! Their quality is unrivaled. I love your crystal clear explanation and balanced discussion of all pro's and cons. I have more than a little technical knowledge, but imagine that even laymen can understand the majority of your video's. I know from personal experience that it's anything but easy to distill so much knowledge on a complex subject into short and understandable teaching. Well done! 👍 I wonder if further improvements in panels, e.g. more bypass diodes, can further reduce the already doubtful net value of optimizers and micro-inverters.

Highest quality thank you

I am so glad I read the video description after watching the video. I had a lengthy reply ready :D Thank you for correcting the errors and covering the highlights optimization and shading effects on solar modules. Although beyond the scope of your video, it is worth noting that while the strings behave as you say, once connected to an inverter, the MPPT will reduce the effects of shading. Some inverters are better than others at this. Along with optimization, module level monitoring is also an advantage of MLPE. You can see everything you discussed in real-time (or close to it). It is great for digging into the details of system operation, especially when homeowners wonder why their "system isn't working." Thanks again, and take my sub!

Having installed Tifo TS4 on all my panels on a large array all I can say as I have shading the performance has been outstanding.

Hi Gary, In your video you indicated that a optimiser bypasses 1 amp when the solar panel is giving 9 amps to give 10 amps. That 10A is then the same as for the other solar panels. The optimiser does not bypass current. Let's say that the solar panel is only producing 15v at 5 amps. 15v x 5A = 75w. What the optimiser does is it converts the 75w power into 7.5V at 10A. 7.5V x 10A = 75w. This then makes the 10A current to be the same as the other good panels. But instead of the voltage in the string being say 30v. it is now only 7.5V. When you add up the total voltage of the string. It will now be less because instead of one panel being 30v it is now only 7.5v.

The best explanation I have seen. Thanks.

Excellent explanation, very simple and easy to understand

Excellent video once again Gary, thank you. I watched for general interest as we fitted Enphase micro inverters to our AC coupled GivEnergy system some time ago. Feels like exactly the right decision for us and we couldn’t be happier with system performance. However, we learned very quickly in our research that “solar” isn’t a “ one size fits all” game. Thanks again 👍

Thanks Gary. You are very informative. I am just starting to learn about solar panels and hope to get an installation done soon.

I have just replaced 2 optimisers that failed in the eighth year after installation. Their tech support guy said that 2 out of 13 was not bad, he had seen worse. He won't hear much from the satisfied customers with no issues. Found out that Solar Edge have a 12 year warranty on the optimiser, but only contribute to labour and scaffolding for the first five years. My installer quoted £1500 + VAT. I did the job myself after bracing my scaffold tower off the wall and using ratchet straps and wall eye bolts to keep it all steady. The tower also makes cleaning easier. I had begun to have issues with some lichen growing on the panels. Have been told thus is more common in the vicinity of silver birch trees. A large one behind us causes partial shading issues throughout the year, so I am still convinced of the benefit of optimisers for my installation.