BTW, the “powered by solar” calculation is simple:
- powered by solar = (usage - from grid) / usage
The “usage - from grid” term is the amount of used energy that was provided by sources other than the grid, i.e the amount of used energy that was sourced by your solar. So that term, divided by the total usage is “powered by solar” percentage. A better term would have been “powered by not grid”.
The grid…all the transmission lines, substations, local lines, etc…requires a lot of investment to keep working. Most of your electricity charges are to support the maintenance of the grid, not the actual cost of electricity generation. The cost of electricity generation is something like $0.03-$0.05 per kWh…the rest of your per-kWh charges are really to pay for the grid (or for peaker generation in the evenings). Us folks with solar and with net metering get to use the grid as a free battery. The electric companies are not going to let us have a free battery at their expense forever (though some of us do have 20+ year grandfathered net metering plans), rather they will be changing their rate plans over time to lessen our benefit of using their grid as a battery. So we should be looking into ways to change our consumption behavior to rely less on the grid battery…we should try to increase our “powered by solar” metric…e.g. shift when we run major appliances to when the sun is shining rather than in the evening.
This might be an interesting read: https://syonyk.blogspot.com/2019/11/what-replaces-net-metering.html