Quick answer: A kilowatt-hour (kWh) is the unit your electricity is billed in: the energy used by a 1,000-watt appliance running for one hour. One kWh costs about 18.2¢ on average in the US and 26.32p under the UK price cap.
kW vs kWh
- Watts (W) and kilowatts (kW) measure power: how fast an appliance uses energy at a given moment. 1 kW = 1,000 W.
- Kilowatt-hours (kWh) measure energy: power multiplied by time. That is what your meter counts and what you pay for.
kWh = watts ÷ 1,000 × hours. A 1,500 W heater for 2 hours uses 3 kWh; a 10 W router for 100 hours uses 1 kWh.
What one kWh does
- Runs a 100 W TV for 10 hours.
- Boils roughly 9 litres of water in an electric kettle.
- Runs a typical new fridge for about 20 hours.
- Drives an electric car about 3 miles.
How much a kWh costs
In the US the national average is about 18.2¢, but state averages ranged from 12.72¢ in Louisiana to 48¢ in Hawaii in July 2026: see rates by state. In Great Britain the price cap sets a maximum average unit rate of 26.32p plus a standing charge of 54.83p a day: see the price cap explained.
The rate on your own bill is always the best figure to use.
Convert and calculate
Frequently asked questions
How many kWh does a house use?
An average US home uses roughly 850 to 900 kWh a month. UK homes use far less electricity because most heat with gas.
Is a kWh the same as a unit?
Yes. In the UK one “unit” of electricity on your bill is one kWh.
How do gas kWh compare?
Gas is also billed in kWh in the UK; in the US it is usually billed in therms, and one therm is about 29.3 kWh.
Worked examples
To turn watts into kWh, multiply the power in kilowatts by the hours used. Three everyday examples:
- A 10 W LED bulb on for 5 hours: 0.01 kW x 5 h = 0.05 kWh, about $0.009 in the US or 1.3p in the UK.
- A 2,000 W hair dryer for 10 minutes: 2 kW x 0.167 h = 0.33 kWh, about $0.06 or 8.7p.
- A 7.2 kW EV charger for 4 hours: 7.2 kW x 4 h = 28.8 kWh, about $5.24 or £7.58.
The same formula works for anything with a wattage label. Our watts to kWh calculator does it for you.
kWh on your bill
Your meter counts kWh continuously, like a car’s odometer. Your bill subtracts the previous reading from the new one to get the kWh you used, then multiplies by your rate. On top of that, most US bills add a fixed monthly customer charge and sometimes delivery charges per kWh, and UK bills add a daily standing charge. That is why your bill is never exactly kWh times the headline rate.
More questions readers ask
What is the difference between kW and kVA?
kVA is used for the capacity of supplies and generators. For appliances and household bills you only need watts, kilowatts and kWh.
How many kWh is a full EV battery?
Most electric cars have batteries of 40 to 100 kWh. A 60 kWh battery charged from empty at home costs about $10.92 in the US or £15.79 in the UK, plus some charging losses.
Sources
- U.S. Energy Information Administration, Electric Power Monthly and Short-Term Energy Outlook.
- Ofgem, Energy price cap.