I talked to a solar installation contractor today and he swore microinverters (an inverter per panel) are more reliable than a single big inverter. This doesn't make sense to me, since there are dramatically more parts in a microinverter system (though the peak currents are a lot lower) and, in general, the inverters will be running hotter than a single inverter would (which is typically located inside).
What is people's experience? This guy claims large solar inverters tend to fail around 10 years, but how many microinverters are even 10 years old at this point to make a meaningful comparison?
It all depends on the quality of the inverter and how hard of a life it has.
An inverter that is running under the roof on a nice shaded side running at half the rated power will have an easier as an inverter that is run to full power on an exposed sunny wall that is pointing towards the sea side where the salty mist covers it. These microinverters having to live up on the roof can't be nice to them either.
But in general well made inverters should be very reliable. The first thing that would go are likely the cooling fans.
Lots of microinverters are indeed more likely to experience a failure because there are more of them. But if 1 inverter fails then say the other 9 keep running so the whole setup is still running at 90% capacity. But if your big single inverter fails you have 0% capacity. So id say they are more reliable in the sense that it takes a lot of failures to seriously degrade the solar array performance.
I think a single big inverter is more sensible. You need to run cables down from the roof anyway. It is in a easier to service spot down there..etc If you are worried about partial shading problems then you can get inverters with multiple MPPT inputs to slice the array up into sections, or use optimizer modules on the panels that contain a small DC/DC converter to balance the shaded panels with the sunny ones.
Yes good points, i cant see microinverters being more reliable, since they will run hot on the roof, their electrolytic capacitors will get boiled off quicker.
Also, if you have a battery storeage, than you want a single inverter so that you can control it not to export power when your house is not using much electricity.....if you have microinverters, they will just shovel power into the grid when your house isnt using much elec.
They probably have polymer capacitors or extra high temp electrolytes calculated at their expected lifetime.
Personally I would go for the cheapest, most servicable option. One big inverter is likely to be cheaper and easier to replace. How do you get to a failed microinverter tucked away between the panels? Over the lifetime of an array of solar panels, the chance that at least one inverter fails is 1.
Still have to add groups in the fuse box to significantly expand, flexibility doesn't seem worth the losses with battery storage to me.
Regarding "are microinverters really more reliable", the general consensus pretty much is they are LESS reliable, so the relevant question is the opposite: are they really less reliable, and if yes, by how much?
The bright side is that failure of one microinverter only brings that one panel down. If you talk to owners of microinverter systems, about every other has one failed microinverter, but it is not a disaster of course. Much more rarely you hear about string inverter failures, but when it happens, it's worse.
The often attributed cause for microinverter failure is the combination of worse efficiency (so more heat), fanless design, and exposure to elements, especially heat behind the hot panels, easily exceeding Ta=60degC, so it is harder to design them to be reliable. Yet, it is entirely possible to design super-reliable microinverters, just harder. String inverters tend to sit indoors in heated/air conditioned room temperatures.
The problem with getting information from contractors / installers is, everybody is selling their favorite systems, so information is always biased. IMHO, it's best to compare $/kWh and ignore technology differences, unless you have a system where every panel faces different direction with lot of shading, in which case you want microinverters.
How about a compromise, parallel connected optimizers
Can directly charge a battery with the bus voltage, the inverter can be designed for a single voltage which will be maintained regardless of the number of panels.
no, more complex, exposure to elements, more connectors, needs management systems eg for shading
Pushed by certain panel mfg and installers.
Experience shows poor reliability vs bulk inv
Of course cheap Chinese junk inverters will be failure prone either micro inverters or bulk.
Check with Daniel at Beyond Oil Solar, a disty for DIYers
Jon
If you do want to have individual panel MPPT and a central inverter you can use optimizer modules:
But doesn't this bring the worst of both worlds? Electronics on the hot roof and a single point of failure. Well... yes and no.
The optimizer modules are indeed power converters that have to live in the harsh roof environment. However the difference is that they now have a lot less work to do. They are just a buck boost DC/DC converter with an input and output range of about 5 to 40V. This means it does not have to deal with mains (high voltage, isolation required, large caps to store between 50Hz cycles, resilience to surges etc..) so it is a lot simpler and produces less waste heat. In a perfectly balanced scenario they can just bypass all of the DC power trough them, making them almost 100% efficient. The more difficult task of turning DC into AC is then done by the classical big central inverter (Where it can have fans, advantage of smoother 3 phase power..etc)
This tech unfortunately looks like it is currently exclusive to SolarEdge because they patented the hell out of it.
Thanks for all the feedback. Yes I think this particular installer has just decided he likes microinverters. I talked to the guy again and turns out they've only been installing microinverters for a couple of years, so his thoughts on reliability don't mean much. They are installing Enphase IQ8 microinverters, which are spec'd to 140F ambient. Hard to know exactly what this means... it regularly gets over 100F air temp here, so it's not a stretch to think the microinverter running at full power on the back of a panel will get up to at least 140F. But 'ambient' should mean outside air temp, right?
For sure these will be operating at the high end of their design range for at least part of the year. Seems much better to have a single big inverter in a garage than all these little inverters cooking up on the roof.
Yes I think this particular installer has just decided he likes microinverters.
Installers, generally, have pet solutions systems that they hitch their wagon to and then modify the components to suit each application.
Not every installer can know all the ins and outs of every type of system. They usually have a deal with one or two eco system's suppliers and to go outside the square, they don't have much supplier discount, or the funds to handle install problems etc.
I'm over simplifying it, and installer -could- deploy any system but the market is often so tight that the customer often only gets offered the easy, cost effective option.
Installers, generally, have pet solutions systems that they hitch their wagon to and then modify the components to suit each application.
This, and also remember installers often have no freaking clue whatsoever about the technology they install. It's actually pretty sad. They can of course (usually!) follow installation instructions, but that's pretty much it. Otherwise than that, an enthusiast who have spent just a few
hours (let alone days!) to read a few technical articles easily surpasses the technical knowledge of a salesman / installer.
There are exceptions to this, of course, but in general, those with high IQ or a lot of interest about technology will rarely take low-level install / marketing jobs, instead they become designers of some kind.
Yes good points, i cant see microinverters being more reliable, since they will run hot on the roof, their electrolytic capacitors will get boiled off quicker.
Also, if you have a battery storeage, than you want a single inverter so that you can control it not to export power when your house is not using much electricity.....if you have microinverters, they will just shovel power into the grid when your house isnt using much elec.
In the UK the default seems to be to put standard inverters in the attic space, which I can certainly believe will be hotter than behind a roof mounted panel. 50-60 C ambient seems pretty plausible on a sunny day, I guess on a roof with solar panels they might lower the inside temperature somewhat.
What is people's experience? This guy claims large solar inverters tend to fail around 10 years, but how many microinverters are even 10 years old at this point to make a meaningful comparison?
I do not have any direct experience with them, but here are my thoughts.
I talked to a solar installation contractor today and he swore microinverters (an inverter per panel) are more reliable than a single big inverter. This doesn't make sense to me, since there are dramatically more parts in a microinverter system (though the peak currents are a lot lower) and, in general, the inverters will be running hotter than a single inverter would (which is typically located inside).
In aggregate micro-inverters should be less reliable because there are more parts to fail and they are more exposed, but they can also afford greater derating and a failure of one micro-inverter is not a catastrophic failure of the system.
What I would like to know is which is more reliable under adverse conditions, like nearly lighting strikes.
They probably have polymer capacitors or extra high temp electrolytes calculated at their expected lifetime.
In military and aerospace applications they may design aluminum electrolytic capacitors out entirely for greater reliability and operating life.
If you do want to have individual panel MPPT and a central inverter you can use optimizer modules:
But doesn't this bring the worst of both worlds? Electronics on the hot roof and a single point of failure. Well... yes and no.
If you are going to have electronics on the roof, then it might as well be microinverters.
Optimisers seem like a bit of a half-arsed solution? But I guess there is a market for half-arsed solutions.
I talked to a solar installation contractor today and he swore microinverters (an inverter per panel) are more reliable than a single big inverter. This doesn't make sense to me, since there are dramatically more parts in a microinverter system (though the peak currents are a lot lower) and, in general, the inverters will be running hotter than a single inverter would (which is typically located inside).
Most I have seen are mounted outside.
Mine was mounted on the other side of the house (outside) so it was in a shaded spot that wouldn't get the harsh afternoon sun on it.
In the UK the default seems to be to put standard inverters in the attic space, which I can certainly believe will be hotter than behind a roof mounted panel. 50-60 C ambient seems pretty plausible on a sunny day, I guess on a roof with solar panels they might lower the inside temperature somewhat.
Mine under the panel is at 100F today on a perfect winter day.
Summer is 141F
There is no way the roof is not hotter than under the panel, as you'd easily have 50C ambient up there in summer.
In the UK the default seems to be to put standard inverters in the attic space, which I can certainly believe will be hotter than behind a roof mounted panel. 50-60 C ambient seems pretty plausible on a sunny day, I guess on a roof with solar panels they might lower the inside temperature somewhat.
Here installers tell you not to use an attic because it gets too hot up there. They usually get installed outside on a wall somewhere near the electrical box so that they don't have to run the AC cables very far(preferably in shade). Sometimes they also get installed inside a garage since electrical panels are often in there.
Here installers tell you not to use an attic because it gets too hot up there. They usually get installed outside on a wall somewhere near the electrical box so that they don't have to run the AC cables very far(preferably in shade). Sometimes they also get installed inside a garage since electrical panels are often in there.
As mentioned, mine was deliberately put on the other side of the house which required huge wire runs both ways. When they installed it I was told that it was well worth the extra cable run to keep the inverter cool, and that I'd thank them for it later. 8 years later, still running fine.
As mentioned, mine was deliberately put on the other side of the house which required huge wire runs both ways. When they installed it I was told that it was well worth the extra cable run to keep the inverter cool, and that I'd thank them for it later. 8 years later, still running fine.
Some good installers right there.
The trend i noticed on youtube is that solar installers love to take shortcuts and do things in the easiest way possible. Like having an inverter with 4 MPPT inputs and instead they just hook up 2 inputs because that means they have to run less cables. (And the guy had panels facing in 4 different directions on the roof, so it would definitely help with partial shading) Especially since the average joe wouldn't be able to know the difference.
As mentioned, mine was deliberately put on the other side of the house which required huge wire runs both ways. When they installed it I was told that it was well worth the extra cable run to keep the inverter cool, and that I'd thank them for it later. 8 years later, still running fine.
Some good installers right there.
The trend i noticed on youtube is that solar installers love to take shortcuts and do things in the easiest way possible. Like having an inverter with 4 MPPT inputs and instead they just hook up 2 inputs because that means they have to run less cables. (And the guy had panels facing in 4 different directions on the roof, so it would definitely help with partial shading) Especially since the average joe wouldn't be able to know the difference.
Yes. Would have been far easier to put the inverter right next to the power board and the solar panels directly above, only a few meters of cable run required. Opposite shaded side of the house is a good 25m away.
If you do want to have individual panel MPPT and a central inverter you can use optimizer modules:
But doesn't this bring the worst of both worlds? Electronics on the hot roof and a single point of failure. Well... yes and no.
If you are going to have electronics on the roof, then it might as well be microinverters.
Optimisers seem like a bit of a half-arsed solution? But I guess there is a market for half-arsed solutions.
I figured that optimisers suit the niche area where a less than optimum string array has been installed for a while, and the removal of shady trees is infeasible. The panels themselves and the inverter are still pulling their weight, a microinverter system seems overkill, doesn't it? And is the guy fitting the enphase microinvs going to be happy connecting them to old panels?
Or am I missing something?