We say kilowatt-hours in Brazil too. Since it's a SI unit, I believe other countries use this too. It's probably because it's a more convenient unit to use when

We say kilowatt-hours in Brazil too. Since it's a SI unit, I believe other countries use this too. It's probably because it's a more convenient unit to use when talking about electrical energy consumption, because 1 watt-hour is the energy consumed by something that has 1W of power running for one hour. One kWh is 3.6 megajoules, so it would be less convenient in this context.