Three solar power proposals

I have three proposals so far for installing photovoltaics on my house.

Proposal	1	2	3
Panel count, brand, power	30 REC Alpha 405W	29 Panasonic EverVolt 410W	29 Q CELLS Q.PEAK DUO BLK ML-G10+ 400W
Panel efficiency	21.9%	22.2%	21.4%
Inverters	30 Enphase IQ8M 330W	SolarEdge	SolarEdge
Power	12.15 kW	11.89 kW	11.6 kW
Annual energy	10,209 kWh	10,450 kWh	10,235 kWh
Price	$35,770	$38,413	$35,579
Price with Fed credit	$26,470	$28,426	$26,328
$ / Watt	$2.94	$3.23	$3.07
$ / Watt, with Fed credit	$2.18	$2.39	$2.27

Some factoids I’ve learned from my self-education…

Prices differ widely by region. This blog post and the numbers in it are coming to you from Seattle, WA USA.

I’m getting proposals from only “full service” local photovoltaic installers. I’d get better economics from a DIY job, but I know my strengths and installing panels on the roof isn’t one of them. I am much happier “writing the check.”

The online conventional wisdom is that DIY jobs come in at $2.50 to $2.75 per Watt nowadays. (That’s before the Federal tax credit.) Professional installer jobs with premium equipment come in at $3 to $3.50 per Watt. These are broad generalities. Prices have been climbing, and are affected by things like wars, embargoes, and supply chain difficulties.

Companies characterize their systems differently, so you can’t blindly compare energy numbers from proposals from different companies. If they differ by a wide margin, sure. If they’re close, it might be caused their different software and estimation tools.

SolarEdge has a single system inverter. It’s more efficient than Enphase in larger installations. But there will be high-voltage DC on your roof, and the entire system goes offline if the inverter fails. Enphase also has a single box on your wall, but it’s a “Combiner” and not an inverter. But how often do inverters fail? SolarEdge has open-source APIs whereas Enphase is proprietary. Both systems have smartphone apps and everyone has opinions about them. Tl;dr: Online cognoscenti argue endlessly about inverters and I’ve decided IDGAF.

REC panels have a 5-year product, performance, and labor warranty. Performance is guaranteed to be at least 92% of initial power in year 25.

Panasonic panels, ditto.

Q CELLS panels have lesser warranties. They have a 25-year production and performance warranty. Performance is guaranteed to be at least 86% of initial power in year 25.