How we calculate running costs
There is no trick to this. An appliance cost is a power rating multiplied by time multiplied by a unit rate, and the only reason published figures disagree is that people use different inputs. Here are ours, in the open.
The formula
Energy in kilowatt hours is the power rating in watts, divided by one thousand, multiplied by the hours it runs. Cost is that energy figure multiplied by your unit rate.
kWh = (watts / 1000) x hours. Cost = kWh x unit rate.
A 2000 watt oil filled radiator running for one hour uses two kilowatt hours. At the current cap rate of 26.11 pence that is 52.2p for the hour.
The UK unit rate we use
We use the Ofgem price cap rate for the period we are in, 1 July to 30 September 2026, which is 26.11 pence per kilowatt hour for electricity on a standard variable tariff paid by Direct Debit. The daily standing charge of 57.19 pence is deliberately left out of appliance costs, because you pay it whether the appliance is switched on or not.
The next cap period, 1 October to 31 December 2026, has been announced at 26.32 pence per kilowatt hour. Gas sits at 7.97 pence. Rates are averages across England, Scotland and Wales, and your region will differ by a penny or two either way. Check the current rates at Ofgem.
The US unit rate we use
We use the national residential average published by the US Energy Information Administration, which for June 2026 is 18.34 cents per kilowatt hour. State rates vary enormously, so the calculator on every page lets you enter your own.
| State | Cents per kWh |
|---|---|
| California | 34.74 |
| Texas | 15.94 |
| New York | 29.49 |
| Florida | 15.10 |
| Pennsylvania | 21.73 |
Check the current rates at the EIA.
Where the wattage comes from
Power ratings come from the maker's specification sheet wherever we can get one. A MeacoDry Arete One dehumidifier draws between 130 and 198 watts depending on room temperature and humidity, and we use that published spread rather than a round number somebody repeated on a forum. Where a manufacturer publishes energy per cycle instead of watts, as washing machines and dishwashers do on the energy label, we use the cycle figure and say so.
What we assume about usage
Every appliance page states the usage pattern behind the monthly figure, for example a tumble dryer at three loads a week or a kettle at six boils a day. Those are stated assumptions, not laws. Change the hours in the calculator and the four output figures change with them.
What we leave out
Standing charges, VAT differences between suppliers, off peak tariffs such as Economy 7, and the small losses in your own wiring. Including them would make the headline number less comparable between appliances, which is the whole point of the site.