Micro Inverters or No Micro Inverters?

[gwichman]

Solar City sure doesn't seem to like them. The salesman makes the following arguments against why SC hasn't deployed them yet:

1. inverters are weakest point in the system. having 15x as many of them only increases the likelihood that you'll have failures.
2. having them up on the roof under the panels where it's hot instead of down on the side of the house in the shade increases likelihood of failure
3. like light bulbs, the more time that goes by, the more of them will fail over time and never at the same time.
4. most installers only offer manufacturer's warranty. manufacturer can elect to repair, replace, or give remaining $ value of it. replacing it is painful as you may have to remove multiple panels to get to the one failed and something you're likely to have to deal with by the time they do start failing.

all seem like pretty good arguments to me.. particularly if you're offering 20 year warranties like SC does.. is there a general consensus in these forums whether this is all just fud?

[solar pete]

I agree with the reasons given.... we only use micros if the customer is adamant that they want them. Or its weird shaped roof or shade issues.

[Mike90250]

Micros solve weird shade issues, Some folks try to justify them using "per panel" reporting. But, they have no advantage other than solving shade problems

[peakbagger]

Micros generally cost more per installed watt but they make it easy for some installers. They are essentially plug and play so a crew can roll up to house with a case of micros inverters, a trailer full of panels and roof rack of racking components and do an install. No worries about string voltage and configuration (Micros do have some limits but far fewer). If there is something like a vent pipe, not a problem just install and let the micro on that panel take the hit. The big cost of a warranty claim is the cost of scheduling and driving to and from the site (truck roll). Since an inverter is the most failure prone part of the system, there are far more possible truck rolls with multiple microinverters mounted in very harsh environment than with a string inverter. I would expect that the labor cost of swapping out a microinverter up on a roof is also higher compared to an inverter change out down on the ground. Many string inverters these days allow the electronics to be changed out without even disconnecting the wires

[SunEagle]

IMO micros work well in places that have a lot of dynamic shade issues but have their drawbacks as mentioned above.

While they also have some good points concerning the simplicity & ease of installing a system it still comes down to the cost/watt and the increased percentage of failure points that may overshadow that simplicity.

[DanS26]

Not only do you have the hardware cost difference between micros and string inverters as mentioned above, but there is a significant difference in wiring cost. In my case with arrays over 300' from the service panel, I was able to pay for my two string inverters just from the savings in wire cost alone. Not only do you have less diameter of wire with higher voltage lines but you have less wires in the trench....3 vs 4.

Also panel monitoring becomes a non-issue if you design with multiple string inverters. Very easy to track down a misbehaving panel.

[solarix]

I totally agree (for once) with Solar City's assessment of microinverters. The risk/reward ratio is simply way too high. I think that installers that are gung-ho on microinverters are going to give the solar industry a huge black eye some day when they start failing willy-nilly causing a big service nightmare.

[ButchDeal]

Micros solve weird shade issues, Some folks try to justify them using "per panel" reporting. But, they have no advantage other than solving shade problems

There is one advantage for micros and that is for small sites that are too small for a string inverter. For us anything under 8 modules is micros (8 is the minimum recomended string size for solaredge).

[bcroe]

And of course having inverters closer to the meter mitigates any over voltage trip problems. Bruce Roe

[steveholtam]

I keep reading that Solar City is working on building their own in-house micro inverters. Until then they will bad mouth them as they don't want to sell the competitors brand.

[J.P.M.]

While I'm in the generally anti - micro camp for the stated reasons and more, I give no credence to anything SolarCity says or does. Good information. Terrible source.

[J.P.M.]

IMO micros work well in places that have a lot of dynamic shade issues but have their drawbacks as mentioned above.

While they also have some good points concerning the simplicity & ease of installing a system it still comes down to the cost/watt and the increased percentage of failure points that may overshadow that simplicity.

In addition to all the other drawbacks of micros, if I had shade issues so bad they needed micros to solve, I'd more than likely have an overall lousy application for PV and therefore probably wouldn't consider PV at all. Not every location is a candidate for cost effective PV, even when properly sized.