I was searching around for a home battery, something to store electricity in to use later on.

I found a 100Ah battery, at 12V output. (I assume DC)

And I was thinking I could get a 12V to 220V inverter (at a high enough W rate, perhaps around 3000W) to be able to use the battery for regular household appliances.

Anyway, I was trying to figure out how many kWh this battery fits and that's where I got confused (being a newbie and all)

According to the formula, 100Ah at 220V = 22kWh.

But 100Ah at 12V = 1.2 kWh.

So it comes out like if you use low power devices you get less electricity?! (stupid assumption, I know)

But help me out here please, with a battery of 100Ah, a 12V to 220V inverter, how many kWh of usable electricity I would get for household appliances?

For example, if I would plug in a 2000W electric grill and leave it on, how many hours would it run on this battery, assuming it goes from full charge to full discharge.

Thank you.