Key learning points

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

Keywords

• Power - the amount of energy transferred every second

• Watts (W) - the unit of power

• Kilowatts (kW) - a larger unit of power; 1 kW = 1000 W

• Joules (J) - the unit of energy

• Kilowatt–hours (kWh) - the unit of energy usage; 1 kWh = 1 unit of energy used

Common misconception