Units of energy

There are two main units of energy:

• Joules - what you’re used to seeing.
• Kilowatt-hours (kWh) - often shown in things like electricity bills.

Joules

One joule is one watt-second, which means it’s the energy transferred when one watt of power is applied for one second.

Kilowatt-hours

One kWh is the energy transferred when one kilowatt (1000 watts) of power is applied for one hour (3600 seconds).

1 \text{ kWh} = 1000 \text{ W} \times 3600 \text{ s} = 3,600,000 \text{ J}

Converting between joules and kilowatt-hours

1 kilowatt-hour (kWh) is equal to 3,600,000 joules (J).

1 \text{ kWh} = 3,600,000 \text{ J}