I am utterly baffled by solar PV. I’m getting a system installed soon. Have been told I need to upgrade my house to three phase power. Trying to work out what I need to:

* power all my house with solar
* store spare energy in batteries
* in such a way that I can use the batteries, use the solar, and charge the batteries during a blackout
* where all the circuits in my house get powered during a blackout

This is super confusing.

@amyworrall Most residential systems *don’t* work without mains power, even if they include battery storage, so the inverter and battery just get connected in parallel to all your consumers, no changes to existing wiring needed.
To make your system act as backup power, you effectively need to have your consumers sit “on the other side” of the inverter, like the downstream sockets of a UPS. Otherwise your battery would be powering your whole neighbourhood in a blackout.

@pmdj @amyworrall this isn’t right - I have a Tesla Powerwall with Backup Gateway and the Gateway has a relay in it that cuts the connection to the grid when it detects the power is out, in order to prevent power going out to the grid.

I don’t understand why you’d need a three phase connection though.

@alex @pmdj Before we knew the three phase requirement, they specked me two Powerwalls. But since Powerwalls aren’t native three phase apparently they have to put them on one phase each, and the three phase inverter they’re trying to spec can’t then charge them during a blackout. I’m trying to figure out what to request they spec to solve this problem, since it can’t be impossible!