The simple formula
Power in watts ÷ 1,000 × hours used × electricity unit rate in pounds = estimated energy cost. For example, a 1,500-watt appliance used for one hour consumes 1.5 kWh. At 28p per kWh, the estimated energy cost for that hour is 42p.
Find the numbers that matter
Look for watts (W) on the equipment label or in the instruction manual. Use your own bill or tariff information to find the cost per kilowatt-hour. Prices shown in examples are illustrative, not live energy tariffs.
Allow for devices that cycle
A thermostatically controlled heater, washing machine or fridge can draw different power levels during operation. A wattage printed on a label is not always the long-term average. A plug-in electricity meter may give a more useful measurement when safe and appropriate.
Use the calculator
Try the free appliance running cost calculator and adjust the hours or days to see how that affects the result.
Open the matching calculator →
Illustrative examples only. Use your own tariffs, measurements and circumstances when making decisions.