The Hidden Downside of Microinverters No One Talks About

With over a decade of experience in the solar industry, I'm sharing my insights on the three key components of a residential solar system: panels, wiring, and inverters. I'll guide you through the factors that really matter when selecting equipment, from panel wattage to inverter technology.

Discover why I believe DC-optimized inverters are the superior choice for long-term reliability and battery compatibility. Plus, learn the importance of choosing a solar installer with in-house electricians for a seamless installation process.

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[bradthesolarguy]

This is a blanket response to all those below saying I’m wrong about the Christmas tree analogy. To those screaming that it’s wrong and dangerously misleading to use this analogy because it no longer applies because of bypass diodes, please keep reading.
The Christmas tree light analogy works perfectly in explaining how solar is wired and installed with a traditional string inverter. Therefore, it is both useful and applicable. To say that it is not as like arguing that explaining how internal combustion engines work is no longer necessary.
Most importantly though, while bypass diodes are effective, they don't eliminate shading issues entirely. They are a protective measure, not a complete solution, and shading can still reduce overall power output. Therefore, modular level electronics that eliminate the shade issues are very useful.
None of that really matters though because today here in the US string inverters aren't widely offered to residential consumers because of the virtual duopoly between Enphase and SolarEdge. Plus, if you just use a string inverter, you lose the advantage of modular level electronics that give you monitoring access at a panel level, which is super important to consumers. If you don’t have that, you won’t know if you have an individual panel out easily.
Also to be 100% clear the most important thing for a consumer to do is use an installer that they trust to do a good job and take care of the system for a long time with a good warranty that covers labor. That’s far more important than an individual technology choice you make. Hope this helps clear things up.

[alexanderlloyd]

I don't know why everybody is knocking you ( probably the installers ! ) I've been watching Web cast's for over two years now and as far as I'm concerned you have just given the best information i have seen to date. Thank you 😊

[ERWINBATHAN]

my apsystems microinverters have been in service since 2014 and still working perfectly fine

[gohi-suretysun]

Brad. As a solar professional who focuses on service and repair of systems installed by others and design and install our own systems, I’m really bummed to hear such an obviously biased video.

I’ve been involved with over 3000 microinverter based system systems and can state unequivocally that microinverters do outlast most other type systems. The failure rate is actually quite close to either SolarEdge or Tigo optimizers. Then the failure point of the string inverter (SolarEdge and Tigo do require a string inverter) is higher than individual microinverters. We actually upgrade the Vers 1 microinverters from 2007-2010 to new Vers 8 units and have to be honest telling the client their old micros are within 20% of original capability which is far better than most string inverters of the same age

Panels? It does make a difference. Temp coefficient, and degradation does vary quite a bit. Sounds like you spent more time selling and managing projects then doing the scientific research onsite testing systems.

Wiring issues are mostly down to wrong wire size and improper JBox work. Otherwise rooftop electrical is very robust even if done poorly. Don’t lie saying that but that’s the truth.

So much is not quite good info

[Bertie..]

There is a 4th inverter option. I installed 16 580w bifacial panels on a Ground mount with 4 NEP BDM 2000 micro inverters. Each inverter supports up to 4 panels. I'm very happy with the performance. Sunny day in March and I'm hitting 65kWh with no clipping. Nova Scotia 🇨🇦

[DorMatt]

My own anecdotal experience as a service technician is that Enphase microinverters and SolarEdge power optimizers fail at about the same rate. SolarEdge issues tons of RMAs on them.

The main advantages, in my opinion, of a DC-optimized system are the ability for DC-coupling combined with module-level monitoring, and also the ability to oversize the DC side, IF your locale has a maximum inverter size (Massachusetts used to have a cap of 10kW AC if I’m not mistaken, and that’s why SolarEdge is so popular there). Under those rules, it’s just way more economical to go with optimizers; a microinverter system would be forced to be smaller with substantially less time in the day at peak output, which over ~25 years REALLY adds up.

SolarEdge has also DOMINATED the 3-phase part of the market for a while. I think this is largely because they saw the need WAY before Enphase, and also (correctly) pointed out the advantages over string inverters.

Only other point I wanted to contest was about modules. Those fail past the 1-year mark all the time, but it’s almost always one bypass diode failing, resulting in production being 2/3 what it should be. This is another area where MLPE really shines - one panel losing 1/3 of itself doesn’t curtail the performance of its neighbors. SolarEdge is actually WAY better than Enphase at detecting bad diodes, too.

[creactioital]

Greetings from Italy. Very helpful, thanks!

[vjoecr]

I'm glad to find out we have another way to avoid string inverters. EEVblog on episode 1426 went over an issue he noticed because a tiny amount of shade on a sting inverter system was causing it to produce significantly less power when the shade was there.

An easy way to think about the problem with a string inverter is to not mix new & old batteries. This is because the batteries with a lower output is going to encourage the other batteries to try to recharge that one battery & the same thing would happen with a string inverter system.

[JimHolder-pkkk]

Interesting perspective. One important item you did not mention is that microinverters at roof level makes a safer system in terms of electrical faults and fire. Up to 600v DC coming through your roof and down to the string inverter is more likely to produce an electrical fire than 240v AC coming down to your combiner panel.

[mb-faze]

Microinverters with no AC on the roof, easy maintenance, easy monitoring and easy upgrading : When I helped a friend install his solar PV on his roof we discussed microinverters etc. The maintenance issue was a big issue for him. I suggested we ran the two MC4 wires from every panel individually to a clean, dry room and install all the microinverters at ground level so they could be monitored and replaced easily. Also, if he did that, he could convert to a string inverter system by just doing a bit of re-connection. Lots of wires but no AC on the roof, easy maintenance, easy monitoring and easy upgrading.

[kreature]

Am I wrong about hating black on black panels? I don't want to have a backing surface on the panels that do nothing but soak up heat and lower the efficiency of my setup.
The extra heat would in theory also increase aging would it not? (If I will get any.)
For me, the choice seem to be about size of panels vs snow load, and if I want a dual-glass version. The bigger panels also do give a lot more power per buck spent, but get unwieldy fast.
Selecting a panel that is as big as possible for the area I am covering seems like my best bet. One area is wide and short allowing only 2 rows of panels, but a longer panel works well there giving high utilization of area while keeping the setup portrait for low bracket cost. Other area is a bit taller but narrower so a bit shorter panel allows 3 rows there. Result is both areas can have 12 panels each. One 495w panels, the other 450w panels. My biggest issue is not being shafted on installation by ppl doing poor work, or on materials. Installers claim the rails cost the same as retail procing for singles at the hw store, which I know is a lie etc. When the total cost of the install becomes larger than the expected total production over next 20 years you know price gouging on gear is happening.

[malk]

Videos like this one do the most damage because the channel presents well, and the presenter sounds like he knows what he's talking about. 80% of what he says is correct, and is valuable information. This makes it far more likely that the 20% of downright false information imparted will be accepted, absorbed and acted upon by viewers.

As others have said, the reality today is that the Christmas light effect really no longer matters. Most panels I'm looking at have three bypass diodes per panel, meaning a 12 panel array is in fact 36 independent solar production zones. Shade one of those zones, and the 35 other zones continue to produce completely normally. You'll only see production drop for the zones that receive shade.

The video also fails to specify that even back in the Dark Ages when bypass diodes were not being used in solar panels, the shading issue only really affects situations where there is shading. I know it sounds obvious, but it needs to be spelled out for some folks. MANY installations, if not most, won't suffer from any shading at all.

So yeah - really, DC optimizers only really make sense to me if you want per panel monitoring. Otherwise they don't seem to be worth the considerable expense. Just get a good set of modern panels and a good string inverter, and you're good to go.

[chrismidyette]

I would really like to know what type of optimizers you're installing. From my experience the failure rate of optimizers are 100 to 1 versus enphase micro inverters. I've been installing solar for almost 30 years now. I have done replacements and repairs more often on DC optimized systems than micro inverter AC system. Just started using Tigo, out of 3 systems I already had to replace optimizers. Approximately 30 years I have probably changed 30 microinverters.

[Dave-orln]

The one issue you didn't address is the cost of swapping out the different inverters when they fail. With an Enphase the company will allow me to do my own install as long as I complete their free online courses and the inverters cost between $159 and $322 depending on which Enphase inverter you chose. On the other hand my gound installed system has two Solaredge inverters which were originally installed by a certified company (because I was getting too old to do the heavy lifting) and when my 10K inverter failed (still under warranty) Solaredge would only allow a company registered with them to evaluate and swap out the inverter. My original installer went out of business so Solaredge will not allow a DIY to activate the inverter to bring it online in a grid tied system. I had already run a diagnostic on the inverter and knew it failed. That required the tech to come to the site twice, once to evaluate that the inverter was dead and then to return weeks later with a remanufactured inverter and install it to the tune of $1800 labor for a total of approximately 30 minutes on site, 10 minutes to evaluate 20 minutes to swap the inverter, unbolt 4 nuts and swap 6 wires and have it update to come on line.

[stephenbrickwood]

The immediate future is using the AC current.

An extra panel will easily overcome a small efficiency loss.

[LifeLongLearner-omjx]

I’m an engineer that actually has designed solar systems from the utility scale to commercial and residential applications for over 15 years.

Dc optimized systems like the ones offered by SolarEdge are garbage. Not because of the technology but because SolarEdge, the largest manufacturer optimizer technology refuses to replace the components when they fail, unless you threaten to take them to court.

Microinverters such as those from enphase have the lowest failure rate of any technology and there’s plenty of data to back that up. They actually test for that.

But for the average homeowner, that doesn’t have a lot of shading of their roof by trees etc, then latest generation of solar panels (with bypass diodes) coupled with a high quality string inverter will be just fine. It’s not usually worth adding 20%+ to the system cost for a 5% improvement in performance.

Also, black on black panels are purely an aesthetic choice but one that makes sense for residential applications as it has wider curb appeal. Most tier 1 manufacturers are making such panels these days at affordable prices.

Finally, the statement about subcontractors is hit or miss. It would be ideal to have all work performed in-house by a company with a long track record of solar specific work. But that’s not the reality everywhere. The more realistic solution is to have a dedicated solar installer that has a sales arm that drives business to them. So, technically it’s not subcontracted since all the work is being performed by the contractor but the consultation/sales part is outsourced because those are two different specialties.

[mrglindsay]

Enphase microinverters for the WIN! Thats what we have and never experianced any issues.

[gohi-suretysun]

The Christmas tree statement is not as clear cut as you say. Even though bypass diodes as some are stating can help. The failure only happens in a string system if a wire is burnt or disconnected. Even broken glass on a panel won’t stop a string from functioning at 70-80% As broken glass doesn’t short cells.

String inverters are great on full exposure systems but perform at the lowest panels production level to some degree. Diodes do help limit this quite a bit.

[CYPanda]

I agree with your position on the central inverter being better for maintenance/repair and having lower fail rates on the optimizers. The amount of people that want the Enphase these days are astounding. Almost everyone we sell too want the Enphase micro's. We tell them we go out and warranty them pretty much weekly for different orphaned systems but no one seems to care. As long as its Enphase, they're happy. The marketing and education behind the micro's give Enphase a huge advantage in the market with all the SolarEdge inverters that do seem unreliable to your average consumer. Best solar system in my opinion is decent made in China panels with the lowest tier Solaredge inverter with S440's. Fastest return on investment and reliable.

[Travatain]

Your video was very informative, you obviously know your solar systems. We are retired and live in the UK and we had a 10 panel system installed less than 2 years ago. It was fine at first then the inverter (Solis) started sending alarms which all stated that there was an arc fault which should be dealt with and these have got more frequent lately. The installers came back once and said they found a faulty connecter under one panel and fixed it but the problem persists so I think that more connectors must be faulty. They want to charge me a lot to come back and fix these so I am waiting for another installer to look at the system. I suspect that these connecters are faulty or have not been correctly wired so my question is - is this a common fault with roof panels or do you think we have just been unlucky? I would appreciate your expert opinion on this.