Energy & cost / FORMULA-BASED TOOL
Electricity cost calculator
Work out energy use and its cost from your own wattage and tariff.
02The working, shownkWh
kWh
Every result has a reason.
Enter your values and calculate to see the result, formula and working here.
kWh = W × hours × days ÷ 1,000Within this model
Constant or time-averaged input power over the entered operating hours and a single unit rate. Excludes standing charges, time-of-use changes and costs outside the entered rate. Default values are examples.
What the numbers mean.
Energy is power multiplied by time. For appliances that cycle, such as a fridge, nameplate power multiplied by all elapsed hours will overstate use. Enter measured average power or the hours actually operating at the specified power.
Formula reference: Virginia Tech · Estimating energy use ↗A worked example
1,000 W × 4 hours × 30 days ÷ 1,000 = 120 kWh. At 25 p/kWh, that is £30.
Validation, precision and limitations