What Your Appliances Actually Cost to Run

The whole calculation is one multiplication

It is worth seeing written out, because it is genuinely this small:

watts ÷ 1000 × hours  =  kilowatt-hours
kilowatt-hours × your rate  =  money

A kilowatt-hour is a thousand watts drawn for an hour, and it is the unit your bill is priced in. The division by 1,000 is the step people skip, and it is the difference between a plausible answer and one that is a thousand times wrong.

Everything else below is bookkeeping around those two lines.

Nothing here is assumed

The wattage comes off the appliance, the hours come from your habits, and the rate comes off your bill. The tool publishes no "typical" figures for any of the three, because typical figures are exactly what makes this kind of estimate worthless — electricity rates vary several-fold between regions and tariffs, and two appliances of the same kind can differ threefold.

⚠️ Get the rate from the bill, not from the tariff. Divide the electricity portion of the bill by the kilowatt-hours it covers. That gives an all-in rate with standing charges spread across your real usage, and it is usually higher than the advertised unit price — sometimes noticeably, in a low-usage household where a fixed daily charge is spread thin.

A 1,500 W heater, three hours a day

Per year	$279.76
Per month	$23.31
Per hour of use	$0.26
Electricity used	1,646 kWh

That last-but-one figure is the one to memorise. Cost per hour of use doesn't depend on how often you run something — only on the appliance and your rate. Work it out once for the handful of things that matter and you can price any decision in your head: another hour of the heater, a longer wash, leaving the dryer going.

⚠️ The label wattage is a maximum, not an average

This is the biggest source of error in the estimate, and it runs one way: it overstates.

Anything with a thermostat cycles. A 1,500 W heater bringing a cold room up to temperature really does draw its full rating — but once the room is warm it switches on and off to hold it there, and may be drawing power only a third of the time. The same is true of fridges, freezers, ovens and air conditioners.

So for that whole class of appliance, enter the hours it is actually heating or cooling, not the hours it is switched on.

Things that run flat out — lighting, a hair dryer, a desktop under load — track their label closely. A 60 W item for five hours a day is $19.74 a year, and that figure needs no discount.

Standby is small, except when it is everything

A device drawing 1 W constantly uses about 8.8 kWh a year. Against a heater that is a rounding error — in the case above, standby is under half a percent of the total.

But standby is charged for every hour you are not using the thing, and there are 8,760 of those in a year. Take something used for half an hour a week that pulls 3 W while off:

Total per year	$4.48
Of which standby	$4.45
Share that is standby	100%

Essentially the entire cost of owning that device is the cost of it sitting there switched off.

Which is why the tool reports standby as a percentage rather than lecturing you about it. The useful move was never unplugging everything — it is finding the two or three rarely-used things that draw real power while off. The percentage tells you which situation each appliance is in.

⚠️ This costs electricity only

Do not use it to compare a gas appliance against an electric one. 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 here would suggest it costs almost nothing to operate.

A fair comparison needs both fuel prices and both appliances' efficiencies at turning that fuel into heat. Heat pumps complicate it further still, because they move heat rather than making it and can deliver more heat energy than the electricity they consume.

Two small things, stated rather than hidden

The year is 52 weeks, not 365.25 days. If you say something runs four days a week, multiplying by 52 answers exactly that question; converting to days would quietly change the pattern you entered. The gap is about a quarter of one percent — far below the uncertainty in any thermostatted appliance's wattage.

Standby hours are 8,760 minus your running hours, floored at zero, so a device you run 24/7 correctly shows no standby cost at all rather than a negative one.

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General information. Your own bill is the authority on your rate.