Electricity Cost Calculator

How electricity costs are calculated

Multiply the wattage by the hours used to get watt-hours, then divide by 1,000 to convert to kilowatt-hours (kWh). Multiply the kWh by your electricity rate to get the cost. For example, a 2,000W heater running for 3 hours uses 6 kWh. At 24.5p per kWh, that costs £1.47.

What is a kilowatt-hour?

A kilowatt-hour (kWh) is the amount of energy used by a 1,000-watt appliance running for one hour. It’s the unit your electricity supplier uses to bill you. One kWh equals 1,000 watt-hours. A 100W light bulb running for 10 hours uses 1 kWh. A 3,000W kettle boiling for 4 minutes uses about 0.2 kWh.

UK electricity rates

The Energy Price Cap from Ofgem sets a maximum unit rate that suppliers can charge on default tariffs. As of early 2024, the cap is around 24.5p per kWh for electricity. Your actual rate may differ depending on your tariff and supplier. Check your latest bill for your exact rate and enter it into the calculator for accurate results.