Nameplate wattage is not always average demand. Use a plug meter or energy label for thermostatic and inverter-driven equipment.
The result is not a supplier bill or quote. Unit rates, standing charges, region, payment method, meter type, tariff, VAT, discounts, debt and support schemes can differ. Use values from the same tariff period and bill for a personal check.
Convert watts to pounds
Standing charges are not allocated to one appliance.
The calculation runs in your browser. Values are not sent to the website.
How the calculation works
kWh = watts ÷ 1,000 × hours; cost = kWh × £/kWh.
Unit-rate energy and daily standing charges are shown separately wherever possible. That prevents a misleading single pence-per-kWh figure.
Worked example in pounds
A 500 W appliance used four hours daily consumes 60 kWh in 30 days.
The example checks the method. It is not a universal tariff or a forecast of your next bill.
What changes the result
The largest differences usually come from:
- average watts
- duty cycle
- hours
- days
- marginal unit rate
How to improve the estimate
Use rates for your region, payment method and meter, including VAT consistently. Match the number of days and do not add standing charges or discounts twice.
Use actual meter readings, separate electricity from gas and compare at least a year for weather-sensitive use. Keep debt repayments and account credit outside consumption cost.
Pre-filled figures are editable, dated reference values with a source.
Frequently asked questions
Will this match my energy bill?
Not necessarily. Regional rates, price changes inside a bill, meter estimates, tariff discounts, debt and rounding can differ.
Does the price cap limit my total bill?
No. It limits rates for covered default tariffs; total cost still rises with energy use.
Sources and review date
Content reviewed on: 2026-08-03.
- GOV.UK – improve home energy efficiency — household efficiency