🔌 Appliance Running Cost Calculator

Enter your appliance's wattage, daily usage hours, and your electricity rate to estimate its running cost per day, month, and year.

Watts and hours become kWh

Electricity is sold by the kilowatt-hour: one kilowatt drawn for one hour. Everything here comes from converting the appliance into that unit and pricing it:

kWh per day = watts / 1000 x hours per day
daily cost  = kWh per day x rate per kWh
monthly     = daily x 30        yearly = daily x 365

The defaults are a 100 W appliance running 5 hours a day at $0.15/kWh. That is 0.5 kWh a day, 7.5 cents a day, $2.25 a month and $27.38 a year.

The month is a flat 30 days, so twelve monthly figures come to $27.00 rather than the $27.38 annual one. The yearly row is the accurate number.

The rate matters more than the appliance

The $0.15 default is a placeholder and nothing more. US state averages run from around 11 cents in Utah and North Dakota to over 40 cents in Hawaii, and California's upper tiers are higher again, so the same appliance can cost four times as much to run depending on where the meter is. Take your own figure off your bill:

your rate = total bill / kWh used on that bill

Dividing the whole bill rather than reading the tariff sheet folds in delivery charges, the standing charge and taxes, which is what you actually pay per unit. Note also that nameplate wattage is a maximum. Heaters, kettles and toasters draw it continuously, but a fridge or a washing machine cycles, so counting the hours it is plugged in badly overstates the cost.

Frequently asked questions

How much does a 100 watt appliance cost to run?

0.1 kWh an hour. At 15 cents a unit and 5 hours a day that is 7.5 cents a day, or about $27 a year. At 30 cents a unit it is $55.

How do I work out my electricity rate per kWh?

Divide the total amount of the bill by the kWh it covers. That gives the effective rate including standing and delivery charges, which is usually a few cents above the headline unit price.

Does an appliance always draw its rated wattage?

Only resistive ones. Anything with a thermostat or motor runs in bursts, so for a fridge or freezer use the annual kWh figure on the energy label instead of hours per day.