Mains electricity

Electrical appliances and devices use different amounts of energy each second, as indicated by their power rating. Power is a measure of the amount of energy used by or supplied to a device in one second. Power is measured in watts (W). Multiplying power of a device in kilowatts (kW) by time in hours (h) gives us the energy used in kilowatt–hours (kWh). Electricity bills are based on the amount of energy units used; 1 unit of energy is equal to 1 kWh.