I'm not sure I care whether it's AC or DC, but it might be nice to have some parallel off-the-grid wiring that comes from a solar-charged battery and will run during a power outage.
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.
Why parallel as opposed to the same wires? There are good answers for this, but for most people what is best second circuit box that runs just the fridge and a few important lights (in my case the well for water). This way you use the same appliances for everything. A parallel circuit implies when the power is out you have to use something different.
As I type this my house is running from a backup generator. The power company has their repair crew in route to whatever the issue is. I'm looking into how/if I can add solar to the system as well.
This gets complicated and depending on your local regulations, may involve an electrician to certify the work. It's similar to the wiring that goes into adding a generator to your home. If you want something a bit less sophisticated but works nonetheless, you can try to wire solar cells, charge controller, and other stuff to a battery, and then just use the battery directly to power devices. Maybe even have two batteries, one being charged, and one being used. I've had friends do this setup in places where they've been renting.
I've been looking at stuff in this space and there are a few options on the market (most out of stock at the moment).
Check out options like the Yeti 6000x. You can buy a transfer switch to go with it for powering a few circuits. The 6kwh battery could run things like your fridge and computers for at least a day.
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.