Using Tesla Solar & Powerwall in San Diego
There's no doubt that I can be a bit of a dunce at times.
I get excited by the idea of helping the environment. And saving some money over the long term makes me happy too. But I can't always be bothered with the details.
And so it was when I complained that Tesla was making a mistake in not letting me buy more solar. Not so much just me of course, but in general.
The problem, it turns out, was that I was optimizing to get off the grid. I was looking to be 100% self powered:
Instead, I should have been thinking about being self powered only at peak times:
My unstated goal was to not pay for power, but I was equating not paying to not pulling power from the grid. As is turns out, SDG&E pays for power sent back to the grid and it does so at the same rates as it charged during specific time periods:
So from 4pm to 9pm, SDG&E charges the highest rate of 53 cents - almost double off peak and almost 6x super off peak rates. And SDG&E also pays out at those rates. Given that information, the obvious thing to do is to optimize to always send power back to SDG&E at peak times.
Tesla has a new(ish) feature to optimize for Time of Use (ToU) plans. This was not yet available when my system was first installed.
With the timing properly configured, I can see the power flowing in an optimized way:
In the above screen, power is flowing from solar right back to the grid. And my batteries are powering my home.
It's clear now that I'm going to be having negative bills for the foreseeable future.
And I probably could have gotten to this state without rushing out to buy more batteries and panels!
Either way, I'm happy to be helping the environment and saving money over the long term.