[ziga]

Lots of variables in sizing a battery system:

- Is your goal battery backup or load shifting?

- How much backup do you need?

- What is your energy usage and peak demand during that time?

Peak demand is a big factor: a single Tesla Powerwall 2 for example has 13.5 kWh of capacity but only 5kW of continuous power. A heat pump or AC can exceed that, which is why many people stack multiple batteries to be able to power their homes. (The new Powerwall 3 can supply more power.)