I've gone through a similar process. The gist of it is that it takes about 6-7 years to recoup the investment, disregarding compound return and opportunity cos

I've gone through a similar process. The gist of it is that it takes about 6-7 years to recoup the investment, disregarding compound return and opportunity cost. You can think of it as buying a bond that pays back in 6-7 years and then getting 23-24 more years of free return (discounting the teardown cost eventually). Here's a more detail approach. 1. Compute your electricity usage. Look at 12 months of electric bill. E.g 800kWh per month (9600kWh per year). 2. Get quotes from the solar vendors. They usually quote in term of 5kW system, 6kW system, or 10kW system. The kW number is the instantaneous electricity the panels generated. Multiply that by hours to get the kWh number. The number of panels doesn't matter because some panels generate more some less. You want the total system output number in kW. 3. Figure out how many hours of useful sunlight a day your house can have. Google Sunroof and other calculators on the web would do it for you. E.g. 5 hours of useful sunlight per day. 4. E.g. with a 6kW system, 6kW x 5 hours/day = 30kWh per day = 900kWh per month = 10800kWh per year. Remember you need 9600kWh/year from 1? This just about covers it, accounting for some loss of efficiency. 5. A 6kW system costs about $14,460–$19,260 in CA. See [1]. Let's say it costs $18,000. Let's say your electric bill is $250/month or $3000/year. $18,000/$3,000 = 6 years to recoup (very simplistic view). Battery is an additional cost, $6000~$10000. [1] https://news.energysage.com/6kw-solar-system-compare-prices-installers/ https://news.energysage.com/6kw-solar-system-compare-prices-...