One kilowatt-hour is the unit of electrical energy and is abbreviated kWh.
To consume 1 kWh, a machine with a constant power consumption of 1 kW (1 kilowatt) has to work for 1 hour.
Worldwide - including in the Netherlands - the kilowatt-hour is the unit of measurement for the electricity bill. The more kilowatt-hours are consumed, the higher will be this bill.