Solar PV pick: Microinverters over central inverter

Our SMA Sunny Boy 6000 central inverter as it was being installed by REC Solar workers in June 2010.

editors-blog-entry3I’m definitely a fan of microinverters, or tiny inverters — inverters, which convert the DC electricity produced by your solar panels to the AC electricity needed, are necessary components of all solar PV systems  — installed on the back of each solar panel. Studies have shown they are more efficient than central inverters.

Moreover, unlike central inverters with microinverters you don’t have to deal with the silliness of solar panel “strings”. Strings mean that the lowest performing panel on a “string” of panels, or a certain number of panels that must be linked together for electrical reasons that I’m not going to get into here, drags DOWN the production of ALL of the other panels on that string.

In fact, if we had to do it again, I would definitely go with a microinverter rather than a central inverter based system (we have a 5.59 kW system with a SMA Sunny Boy 6000 central inverter).

Microinverters were really only beginning to take off three years ago when we had our system installed, but they’ve grabbed more and more the market here in the U.S.

enphaseMicroinverters more up front
While they’re a bit more expensive up front (perhaps 25 percent), microinveters will help make your system more productive in more ways than one.

For example, if you have consistent snow cover issues, as we do in the winter (snow IS a shading issue, a very serious one), microinverters ensure that as the snow slowly, and unevenly, melts off your panels that the ones that are still snow-covered don’t drag down the production of those which are not.

Jim Jenal, CEO of Run on Sun, a solar installer in the Pasadena, Calif. area, recently wrote about the advantages of microinverters. I definitely recommend anyone considering having a home solar PV system installed, read Jim’s whole entry, which you can find here. Here’s a great  excerpt ==>

“Our testing shows a 15 percent improvement in yield [with microinverters] and that goes even higher depending on the amount of shading at the site. Beyond that, the microinverter comes with a 25-year warranty, the string inverter only 10. Which means for the client, they are going to have to spend an additional $2,800 or so ten years down the road when their string inverter dies (sooner if it is baking in the sun). All of which argues quite convincingly that the microinverter is the better deal for the installer’s client – which last time we checked was supposed to be the point of the exercise.”

Long-term savings
The bottom line: Give microinverters a serious look, even if your solar installer pushing you toward a central inverter.

For example, I definitely got the sense our solar installer — which I am very satisfied with, — REC Solar, was biased toward SMA central inverters at the time we had our system installed in 2010. I suspect one reason may be that solar installers commit to, or perhaps have already bought, large numbers of central inverters in volume to get a lower price.

I’m not going to say everyone who’s having a residential system installed must go with microinverters.

But, honestly, I can’t think of a good reason why you would not pick microinverters over a central inverter except, perhaps if you’re not planning on being in your home at the 12-year mark when that central inverter that “saved” you money over microinverters in the beginning has to be replaced, to the tune of several thousand dollars. Meanwhile, if Enphase microinverters live up to their billing, they’ll be ticking another 12 years before they might have to be replaced.

Related articles–>