In this guide
Unit rate and standing charge
Your unit rate is the price for each kilowatt-hour used. A standing charge is a separate daily amount. For appliance comparisons, enter the unit rate including VAT, in pence per kWh. Do not add the standing charge to that number.
Convert watts into kilowatt-hours
Divide watts by 1,000 to obtain kilowatts, then multiply by hours of operation. A 100 W device used for five hours consumes 0.5 kWh if it draws that power throughout. At an illustrative 25p per kWh, that is 12.5p.
Multiple rates and variable usage
If your tariff has different rates at different times, calculate each time period separately and add the costs. Devices with compressors, thermostats or cycles do not necessarily use their rated power continuously. An energy label showing kWh per cycle is more useful for a cycle-based estimate.
Use your bill, not a national average
Our calculator starts with an example rate. Replace it with your own supplier’s rate for the relevant period. Estimates do not include standing charges, discounts or other bill adjustments.
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