Kilowatt per hour or kWh is how Eskom is billing you on the number of kilowatts or 1000watts you consume in an hour, billed per month. This makes it easy to determine your total energy consumption to calculate your total battery capacity for a battery bank.
We use voltage and Amp hours to calculate the total capacity.
Voltage x Amp-hour = Capacity in Watt-hours.
If we use a 12V battery it will be like this:
12V x 75Ah = 900Wh.
A 12 Volt battery running for 75 Amp-hours produces 900-watt hours or 0.9kWh of energy.