quote:

10% a year is a nice return. I don’t know anyone who assumes they can get that consistently.

The worst 20 year rolling index of the S&P500 is 6%, while the best is 18%. I debated using 10%, but the majority of 20 year rolling indexes were above 10%. I went with the 10% thinking it balances the risk of a 20 year time frame for the solar power system. In other words, if the solar power system doesn’t at least give me a 10% return, it’s just not worth the risk vs leaving the money in the S&P500.

It doesn’t change my unclearly made point that the calculation has too many variables and the time frame is too long for an off grid solar powered system to make sense for me. Net metering comes close in some cases because it eliminates the batteries, but then it’s useless in a power outage.

I’ve got a 50amp breaker interlock on the Florida house. It’s great as an occasional emergency power solution. The Michigan house has an automatic transfer switch with load shedding for the 22kW standby generator. It works great when we aren’t there to keep the air handler and sump pumps running.

I can’t imagine spending tens of thousands of dollars on a solar powered system and not using a transfer switch. I don’t know what benefit an interlock has over a transfer switch.

One of the things I don’t understand with regard to Tesla is that their battery is about $11k apiece for about 11kW.

You can buy a model Y with about a 90 kW battery for about $50K ….

What would be the most effective is if you could use your EV to power your house in the event of a blackout…

I'll be using lithium iron phosphate batteries.