A kilowatt-hour (kWh) is a unit of energy. It is the amount of energy used when something with a power of one kilowatt (1,000 watts) runs for one hour. Suppliers charge for gas and electricity per kWh, which is why bills often call it a “unit”.
kW and kWh
A kilowatt (kW) measures power: how fast energy is used or produced at a given moment. A kilowatt-hour measures energy: how much is used or produced over time. The link is simple:
energy (kWh) = power (kW) × time (hours)
| Example | Power | Time | Energy |
|---|---|---|---|
| Kettle | 3 kW | 10 minutes | 0.5 kWh |
| Electric heater | 2 kW | 3 hours | 6 kWh |
| LED bulb | 10 W (0.01 kW) | 100 hours | 1 kWh |
| Microwave | 1 kW | 15 minutes | 0.25 kWh |
The same logic applies at larger scale. Power stations and wind farms are rated in megawatts (MW) or gigawatts (GW), and their output is counted in megawatt-hours (MWh), gigawatt-hours (GWh) or terawatt-hours (TWh). One MWh is 1,000 kWh.
Typical UK household use
Ofgem uses typical domestic consumption values to express the price cap as an annual bill. From 1 July 2026 these are:
| Fuel | Typical use per year |
|---|---|
| Electricity (single-rate meter) | 2,500 kWh |
| Electricity (multi-register meter, such as Economy 7) | 3,400 kWh |
| Gas | 9,500 kWh |
They replaced the earlier figures of 2,700 kWh for electricity and 11,500 kWh for gas, because household use has been falling.
Why it matters
Your bill is mainly the number of kWh you use multiplied by the unit rate, plus a daily standing charge. Knowing an appliance’s power and how long it runs lets you estimate its share of the bill. Your own use may be very different from the typical figures, so your meter readings are a better guide.
Read more: Which appliances use the most electricity? UK running costs explained.