A kWh, or kilowatt-hour, is a unit of energy. On an electricity bill, it shows how much electricity you have used over time.
The easiest way to understand it is this: if an appliance uses 1 kilowatt of power for 1 hour, it has used 1kWh of electricity. Related Calculatorz pages include an EV tariff.
How to calculate kWh
You calculate kWh by converting watts into kilowatts, then multiplying by time used.
kilowatts = watts ÷ 1,000
kWh = kilowatts × hours used
For example, a 2,000W electric heater is 2kW. If it runs for 3 hours, it uses 6kWh.
kWh examples at home
The actual kWh used depends on the appliance power and how long it runs.
Kettle
A kettle may use high power, but only for a few minutes, so the kWh per use can still be small.
Electric heater
A heater can use a lot of kWh if it runs for several hours, especially at high wattage.
Fridge-freezer
A fridge-freezer cycles on and off, but it matters because it runs every day.
Solar panels
Solar generation is often measured in kWh, which can then be used at home or exported.
Why kWh matters on your energy bill
Electricity cost is usually based on the number of kWh used multiplied by the electricity unit rate. Your bill can also include a daily standing charge and other adjustments.
electricity cost = kWh used × unit rate
This is why reducing kWh can lower the usage part of a bill. It will not remove standing charges, but it can reduce what you pay for electricity consumed.
kWh vs kW
kW and kWh are related, but they are not the same.
| Term | Meaning | Simple example |
|---|---|---|
| kW | Power at a point in time. | A 2kW heater is using power at a rate of 2 kilowatts while running. |
| kWh | Energy used over time. | A 2kW heater running for 3 hours uses 6kWh. |
FAQs
What does kWh stand for?
kWh stands for kilowatt-hour. It is a unit of energy used to measure electricity consumption.
Is kWh the same as kW?
No. kW measures power, while kWh measures energy used over time.
How many watts are in 1kWh?
1kWh is the energy used by a 1,000W appliance running for 1 hour.
Why is kWh important?
Your usage cost is based on how many kWh you use multiplied by your unit rate.