Calculate appliance electricity cost

How it works

Watts ÷ 1,000 × hours gives daily kilowatt-hours, which are multiplied by the entered price per kWh. Weekly, nominal 30-day monthly, and 365-day yearly figures are calculated from the unrounded daily amount rather than by multiplying displayed rounded totals.

• Wattage, hours, and tariff are required because loads, duty cycles, contracts, and regions differ.
• Ofgem separates per-kWh unit rates from the daily standing charge, which is not included here.

Worked example

											Watts: 100
Hours per day: 5
Price per kwh: 0.25
										

												K wh per day: 0.5
Daily cost: 0.125
Weekly cost: 0.88
Monthly cost: 3.75
Yearly cost: 45.63
											

When to use this

Space-heater labels support fixed-session estimates, routers and NAS devices model near-continuous loads, and plug-in meters supply average watts for refrigerators or dehumidifiers.

Edge cases

• A thermostatic 2,000 W heater does not draw its rated power through every elapsed hour; use metered average watts or active hours to represent cycling.
• Economy 7 and other time-of-use tariffs need separate rate-period calculations unless their usage has already been reduced to one weighted unit price.
• Standing charges, VAT treatment, rebates, and tiered rates are absent, so the amount is a consumption charge rather than a complete bill.

References