Help me decide - Microinverters?

[sensij]

The SMA TL series was just launched in 2008, and the US model came in 2013. "Transformerless" represented a major architecture change from previous generations. Anyone trying to sell you on SMA real-world reliability over periods longer than 7 years is making stuff up.

[bru102]

I did an Enphase M250 self install (another engineer!). It's working well and the monitoring is great... looking at individual inverter output, AC & DC voltage per panel, etc....even dB noise levels affecting communication.

I considered SolarEdge and ran into a corner... they spec'd a 1% max voltage AC voltage drop, so their support folks recommended my inverter (for a 13kw system) be placed in the garage, 300ft from the arrays. But then I ran into their round trip DC wire limit for signaling. In retrospect, I'd design for 2% drop as I did with Enphase, and mount the inverter at the arrays with a couple "nanostation" wifi bridges to get the data to the house. (Seems like pro installers use reasonable wire size and ignore the voltage drop recommendations, probably going as high as 3%)

Microinverters are great, but they cost more to manufacture, hence Enphase's financial struggle to meet SolarEdge's price points. IMO SolarEdge offers similar (almost but not quite) safety, performance, and diagnostic advantages at lower manufacturing cost.

[captaindomon]

One issue is that it is VERY difficult to get backup power with microinverters. With the SMA TL-US inverters it comes for free (at least while the sun is out.)

I agree with this. I chose an SMA TL string inverter because I wanted the 1500 watt emergency power supply.

[TimeOrMoney]

Well, everyone, thanks for all the replies! After doing some construction cost calculations and running PVwatts for the site, it now seems that my Southwest facing rooftop might generate power so close to the remote South facing ground mount that I'll save money even with adding a couple of panels. No trenching, long runs, footings. Wow! What a great bunch of free tools there are out there! I had no clue how little you lose 45 degrees off optimum.

So now I'm rethinking everything. It's a big two story with little to no shade right now. Still need to evaluate future tree growth shading, but I think it'l be manageable.