kWh (kilowatt-hour)
A kilowatt-hour is the amount of energy used by a 1 kW appliance running for one hour.
What it is
A kilowatt-hour (kWh) is the standard unit of energy on gas and electricity bills. Using 1 kW for one hour is 1 kWh. A thousand kWh is a megawatt hour (MWh).
Where you will see it
- On every bill, as the amount used and as the price per kWh (the unit rate).
- In your annual usage estimate, which drives quotes.
- In tax and eligibility tests, such as the microbusiness limits and the Climate Change Levy.
Why it matters
Almost every cost is built on kWh, so you can compare suppliers only by comparing p/kWh together with the standing charge. The thresholds that determine your protections are in kWh a year: below 100,000 kWh of electricity or 293,000 kWh of gas can make you a microbusiness. The Climate Change Levy is 0.801p/kWh from 1 April 2026.
Gas meters read volume, not kWh
Many gas meters show cubic metres. To convert: volume x 1.02264 (the standard volume correction) x calorific value (often around 39 to 40 MJ/m3; use the figure on your bill) / 3.6. For 1,000 m3 at a calorific value of 39.5: 1,000 x 1.02264 x 39.5 / 3.6 = about 11,220 kWh. Your bill states the actual calorific value; use our gas units to kWh converter for the exact sum.
Example
A shop using 20,000 kWh at 28.4p/kWh pays 20,000 x £0.284 = £5,680 on units alone, before standing charges, CCL and VAT. See how to calculate your annual cost.
Related terms
kW and annual quantity.
Common questions on this topic
Sources
General information only. Energy prices, rules and supplier terms change; check the latest position with your supplier, Ofgem or the Energy Ombudsman before you act.