Question

What is a kilowatt-hour?

Answer 1

First of all, kilowatt-hour od kilowatt hour has many symbols: kW·h, kW h or kWh. It is a unit of energy equal to 1,000 watt-hours, or 3.6 megajoules.

Very simple:
If the energy is being transmitted or used at a constant power over a period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time in hours.

It is commonly used as a billing unit for energy delivered to consumers by electric utilities.