Best solution for non-solar backup?

[neoprema]

You also mentioned 3 phase & i think that opens some different problems than just a single phase setup.
eg: You need a 3 phase inverter or x3 single phase inverters.

So this is what confuses me - we have 3 phase yes.

but the generator is a single-phase, and yet runs almost the whole house with no issues? except geysers. How is it doing that?

 

[TheChamp]

So this is what confuses me - we have 3 phase yes.

but the generator is a single-phase, and yet runs almost the whole house with no issues? except geysers. How is it doing that?

It could be connected to just a single phase or you could be having some very advanced switchgear between your house wiring and the generator, a good electrician will be able to tell what is happening, but generally people just connect their backups to one phase that has the essential loads.

 

[Saba'a]

its so seamless i don't even register that Eskom has been cut / reconnected. Lights don't flicker, motors (AC or pool) don't rev up or down.

In terms of going over - i think it depends on how much beyond the rated - will try find the spec sheets for you for the 5 and 8kw.

Apparently it does flicker. But somehow I never notice the lights flickering.

 

[SauRoNZA]

But are there inverters designed for only this role? Not expecting a solar panel as well? Or do you just not connect solar to them if you don't want it?

I see there's some by Sunny, Mecer, RCT etc. What I can't find is a calculator to say ok at 8kva, you will need X batteries to run for 4 hours.

KVA equals how much you can use at any one time without something tripping.

See it like bandwidth. Or how fat the hose is to let the water through t.

Kwh = batteries = the same units on your power meter. The amount of water that you can run through the pipe before it goes dry.

It’s deeply unlikely you need two Powerwalls to stay online for a few hours.

Simply look at your daily consumption on your prepaid meter or average it out per month and work it back from there how much you’ll need realistically.

One single Powerwall would do then job most likely.