[stephen_g]

I’m looking at building a system based on a Victron Multiplus II inverter/charger - first an off-grid system for a friend who has bought a large property with no power line hookup, and then my own system at home. It’ll just hook into my existing wiring.

They have an automatic transfer switch built in for anti-islanding (your mains entry goes through it), so it disconnects you from the grid if it goes down but your local side still operates. I think it can also have two AC outputs, one for loads powered by either grid or battery, and one that is only on when the grid is present (if you have a grid). You can use any type of battery so you’re not locked in (LiFePO4 are some of the best at the moment).

I have an AC solar inverter and 5kW of panels on my roof, which would be about enough, but I’m going to add another four panels (bit less than 1.5kW) that are DC-coupled through an MPPT charter (Victron SmartSolar MPPT) to solve the bootstrap problem for prolonged outages (which are very rare here, but still). Not sure if that’s the normal term, but I mean where the batteries run out, so without the grid to put some charge in them, the inverter/charger can’t produce an AC waveform for the PV inverter to lock to, so the PV inverter won’t switch on. Having some solar on the DC charger lets that work.