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This calculator turns an appliance's power draw and daily use into the cost per day, month and year, along with its annual energy consumption in kilowatt-hours.

It is useful for spotting the expensive devices in your home, comparing an old appliance against a more efficient new one, or estimating what a heater, fridge, PC, air conditioner or pool pump adds to your bill.

The maths is simple: energy per day is the power in kilowatts times the hours used, and multiplying by your price per kilowatt-hour gives the daily cost, which then scales to the month and year.

An appliance's wattage is usually printed on its type label, the plug or in the manual, in watts. For devices that cycle on and off, like a fridge or a thermostat-controlled heater, use the average power rather than the peak.

Standby and phantom loads add up too: devices left in standby draw a few watts around the clock, which over a year can cost real money across many gadgets, so it is worth checking always-on devices.

Electricity prices vary by country, tariff and year, so enter the rate from your own contract for an accurate result. Everything is calculated in your browser.