Appliance Running Cost Calculator

How this is calculated

THE WHOLE THING IS ONE MULTIPLICATION, and it is worth seeing written out: watts / 1000 x hours = kilowatt-hours, and kilowatt-hours x your rate = money. Everything else here is bookkeeping around that. A kilowatt-hour is one thousand watts drawn for one hour, which is the unit your bill is priced in, and the division by 1,000 is the only step people usually miss. ⚠️ EVERY NUMBER HERE IS YOURS - NOTHING IS ASSUMED. The wattage comes off the appliance, the hours come from your habits, and the rate comes off your bill. This tool publishes no 'typical' figures for any of them, because typical figures are exactly what makes an estimate like this useless: electricity rates vary several-fold between regions and tariffs, and two appliances of the same kind can differ by a factor of three. GET THE RATE FROM THE BILL, NOT FROM MEMORY. Divide the total cost of the electricity portion by the kilowatt-hours used, and you have your real all-in rate including standing charges spread across your usage. The headline unit rate on a tariff usually understates what you actually pay per unit. If your tariff has peak and off-peak periods, run the tool twice. THE LABEL WATTAGE IS A MAXIMUM, NOT AN AVERAGE - and this is the biggest source of error in the estimate. Anything that THERMOSTATS cycles on and off: heaters, fridges, freezers, ovens, kettles held warm, air conditioners. A 1,500 W heater holding a room at temperature might draw its full rating only a third of the time, so the honest way to use this tool for that class of appliance is to enter the hours it is actually HEATING rather than the hours it is switched on. Things that run flat out - lighting, a desktop computer under load, a hair dryer - are much closer to their label. STANDBY IS SHOWN SEPARATELY BECAUSE THE SURPRISE RUNS BOTH WAYS. A device drawing 1 W constantly uses about 8.8 kWh a year, which is trivial. But standby is charged for every hour you are NOT using the thing, and there are 8,760 hours in a year - so for something used rarely and left plugged in, standby can genuinely exceed the running cost. The percentage output exists to tell you which situation you are in rather than leaving you to assume. ⚠️ THIS COSTS ELECTRICITY ONLY. A gas oven, a gas dryer or a gas boiler burns fuel priced entirely differently, and their electrical draw is only the fan, ignition and controls. Do not use this to compare a gas appliance against an electric one - that comparison needs both fuels' prices and both appliances' efficiencies, and it is a different calculation. A YEAR IS 8,760 HOURS AND 52 WEEKS HERE. Using 52 weeks rather than 365.25 days keeps the weekly pattern you entered intact; the difference is about a quarter of a percent, far below the error in the wattage figure itself.

Common questions

Where do I find the wattage?

On the rating plate - usually a sticker on the back or underneath, or a moulded panel near the power inlet. It will show either watts directly or a voltage and an amperage, in which case multiply them: 120 V at 12.5 A is 1,500 W. The manual and the manufacturer's spec page carry the same figure. If a device has several modes, the plate usually shows the maximum, which is the one to be careful with - see the next answer.

Why does my heater cost less than this says?

Because the label wattage is a maximum, not an average, and anything with a thermostat cycles. A 1,500 W heater bringing a cold room up to temperature draws its full rating - but once the room is warm it switches on and off to hold it there, and might be drawing power only a third of the time. The same applies to fridges, freezers, ovens and air conditioners. For that class of appliance, enter the hours it is actually HEATING rather than the hours it is switched on. Appliances that run flat out - lights, a hair dryer, a desktop under load - track their label closely.

What rate should I enter?

Your real one, worked out from the bill rather than remembered from the tariff. Take the electricity portion of the bill, divide it by the kilowatt-hours it covers, and you get an all-in rate that includes standing charges spread across your actual usage. That figure is usually higher than the advertised unit rate, sometimes noticeably so on a low-usage household where a fixed daily charge is spread thin. If you are on a time-of-use tariff, run the tool twice - once at the peak rate and once off-peak - because for a big appliance the difference between the two is often the whole decision about WHEN to run it.

Is standby actually worth worrying about?

It depends entirely on how often you use the thing, which is why the tool shows it as a percentage rather than telling you. A device drawing 1 W constantly costs about 8.8 kWh a year, which is a rounding error next to a heater. But standby is charged for every hour you are not using it, and there are 8,760 of those in a year - so for something used for an hour a week and left plugged in, standby can be most of its annual cost. The useful move is not unplugging everything; it is finding the two or three rarely-used things with a real standby draw.

Can I use this to compare an electric appliance against a gas one?

No, and that comparison is a genuinely different calculation. This costs electricity only, at the rate you supply. A gas oven, dryer or boiler burns fuel priced per therm or per cubic metre, and its electrical draw is only the fan, ignition and controls - so running it through this tool would suggest it costs almost nothing to operate. A fair comparison needs both fuel prices and both appliances' efficiencies at converting that fuel into heat, and heat pumps complicate it further by moving heat rather than making it.

Why does the year use 52 weeks rather than 365 days?

To keep the weekly pattern you entered intact. If you say a thing runs four days a week, multiplying by 52 weeks answers exactly that question, whereas converting to days and multiplying by 365.25 quietly changes the pattern. The gap between the two is about a quarter of one percent - far smaller than the uncertainty in a label wattage, which can easily be out by a third for anything thermostatted. Standby uses 8,760 hours, the full year, minus the hours you said it was running.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Appliance Running Cost Calculator at https://www.bfcbrilliance.com/tools/appliance-running-cost-calculator.

What I entered:
- Appliance wattage (W): ___
- Hours used per day (h): ___
- Days used per week (days): ___
- Your electricity rate ($/kWh): ___
- Standby draw when not in use (W): ___

What it calculated:
- Total cost per year: ___
- Per month: ___
- Cost per hour of actual use: ___
- Electricity used per year: ___
- Of that, standby costs: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

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