Good thing you get to use all of the produced kWh. I don't know about LADWP but for SCE, the buy back rate is very cheap:So I should have used actual numbers.
1. My house uses approximately 25,000 kWh per year. Over 20 years that’s 500,000 kWh. At LADWP 27 cents, that’s about $125k.
2. My 16.32 / 3 PW system will cost a around $90k over the same 20 years. That’s because it will produce at least 25,000 kWh per year and I get to use all of those kWh. So it’s 27 cents v 19 cents, or an average bill of over $500 vs cost of $300.
3. A solar roof would cost more, but as I said, you get to subtract the cost of the new roof, I stead of just paying for the new roof.
I think other factors even out:
Yes, the system may become less efficient, but power costs could increase by more as a percentage.
The system could also last for more than 20 years, at which point it is however many years of truly free electricity.
So that is with PWs. Without PWs the system cost is about half.
Everyone’s energy costs vary (captain obvious!) but since the cost of the system does not vary, I see no way around doing the calculation for oneself.