How appliance running cost is calculated
- Rated power in watts is divided by 1,000 to convert it to kilowatts.
- Power is multiplied by operating time to estimate kWh per use. If you enter measured kWh instead, that figure is used directly.
- Energy use is multiplied by your electricity unit rate. Weekly use is projected to 52 weeks for the annual estimate.
When rated watts can mislead
Fridges, freezers, heat-pump dryers and thermostatically controlled appliances cycle on and off. Their maximum wattage may therefore overstate long-run consumption. A measured kWh figure is usually better.
Standing charges
The daily standing charge is excluded because it normally does not change when you switch one appliance on or off. The relevant marginal cost is the extra kWh used.
Worked example
A 2,000W heater used for one hour consumes about 2kWh. At 26.11p/kWh that is about 52p before any thermostat cycling is considered.
Methodology & source
The maths is pure energy arithmetic. The prefilled unit rate is an editable Ofgem GB average Direct Debit reference for the current price-cap period.