Appliance Running Cost Calculator

How the Appliance Running Cost Calculator works

Appliance running cost calculator: watts to dollars

Power in watts divided by 1,000 is kilowatts; kilowatts times hours is kilowatt-hours, which is what the bill charges for. A 2,000 W fan heater running for four hours uses 8 kWh, and at 30 cents per kWh that is $2.40 a day, $16.80 a week, about $73 a month and $876 a year if it ran every day. The page does this multiplication and scales it to each period, using 365.25 days for the year and a twelfth of that for the month. The wattage is on the rating plate on the back or underside of the appliance, on the plug pack for small electronics, or in the manual; the list on the page gives typical figures for common appliances when you do not have the label to hand.

Rated power versus average power

The rating plate shows the maximum draw. Some appliances run at that figure the whole time they are on — a kettle, a fan heater, an incandescent bulb. Others cycle: a fridge's compressor runs perhaps a third of the time, an oven's element switches off once it reaches temperature, and an inverter air conditioner ramps down as the room approaches the set point. For those, the average draw is well below the plate figure, and the list on this page uses averages for the fridge and freezer for that reason. A better source for cycling appliances is the energy label's yearly kWh figure, which you can divide by 365 and enter as if it were a one-hour daily run at that many watts, or the actual reading from a plug-in power meter, which costs less than a month of running most heaters.

What actually costs money

Heating and cooling dominate. Anything that makes heat from electricity — fan heaters, oil columns, electric hot water, dryers, ovens — draws a lot of power, and the ones that run for hours cost the most. A reverse-cycle air conditioner produces three to four units of heat per unit of electricity, so despite its higher wattage it heats a room for a third of the cost of a resistive heater. A heat-pump dryer uses a third of the power of a vented one. At the other end, standby loads and small electronics matter less than people think: a Wi-Fi router on all year at 10 W is about $26. For a whole-house figure from the meter rather than one appliance, the electricity cost calculator includes the daily supply charge.

The table

The table below the result lists every appliance in the list at your tariff, with the cost per hour and per year at the hours you entered. It is meant for comparison rather than a bill estimate: a kettle does not run four hours a day, but seeing that it costs 66 cents an hour against 3 cents for a fan explains why boiling only the water you need makes a difference and leaving the fan on does not.

Appliance running cost per hour

Typical wattage for each appliance at a tariff of 30 cents a kWh.

Typical power draw and cost per hour of running at 30c per kWh

Appliance running cost formula and worked examples

The formula: kWh = watts × hours ÷ 1,000; cost = kWh × tariff per kWh. Daily, weekly and yearly figures multiply up by the hours a day and days a week the appliance runs.

First example. A 2,000 W kettle used for 15 minutes a day uses 0.5 kWh; at 25p per kWh that is 12.5p a day and about £45.63 a year.

Second example. A 100 W fridge freezer that cycles on for about 10 hours a day uses 1 kWh a day — 365 kWh a year, or £91.25 at 25p.

How many kWh does an appliance use? Its wattage in kW times the hours it runs: a 3 kW heater for 4 hours uses 12 kWh.

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