Running cost calculator

What it costs to run

See what an appliance or a habit costs per month and per year, and what a more efficient replacement would save you.

New to this? See how it works ↓

Your numbers · replace with your own

Replace with the rate on your bill

Compare with a replacement (optional)

Your result

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Use per month
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Cost per month
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Cost per year
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An illustration based on the numbers you entered, not a forecast and not advice.

Assumptions & limits

  • Uses the rated power as if the device drew it constantly while on; many appliances cycle, so real use can be lower.
  • The electricity price is the per-kWh usage charge from your bill; fixed monthly charges aren't included.
  • Seasonal use is approximated by the number of months you enter.

How it works

From watts and hours to dollars a month

An appliance's label gives its power in watts, your bill gives a price per kilowatt-hour, and what you want to know is the cost per month. The electric mode multiplies the two through the hours you use the device: power in kilowatts, times hours a day, times days a month, gives energy in kWh, and energy times the price gives the cost.

To test a replacement, add the power of the alternative and, if you like, its price. The calculator shows both side by side, the saving per year and how long the replacement takes to pay for itself; one click carries these numbers into the payback calculator. The other mode covers anything measured in units, such as litres of water, gallons of fuel or washing cycles, from the amount used each time, the number of uses a month and the price per unit.

The power on the label is treated as if the device drew it the whole time it is on, while many appliances cycle and use less. The electricity price is the per-kWh usage charge from your bill, without fixed monthly fees. Seasonal use can be approximated by the months you enter. Nothing you enter is stored or sent anywhere.

Formula

Electric
kwh_month   = watts ÷ 1000 × hours per day × days per month
cost_month  = kwh_month × price per kWh
cost_year   = cost_month × months per year

With an alternative
saving_year = (cost_month − cost_month_alternative) × months per year
payback     = alternative price ÷ saving_year      (years)

Water, fuel, other
units_month = used per use × uses per month
cost_month  = units_month × price per unit
cost_year   = cost_month × months per year

Worked example

A 1,500 W heater used 5 hours a day

A 1,500 W heater runs 5 hours a day for 30 days a month, all 12 months, on electricity at $0.17 per kWh. You compare it with an 800 W replacement that costs $200.

Worked example, step by step
Step Result
Energy per month 1.5 kW × 5 h × 30 days = 225 kWh
Cost per month 225 kWh × $0.17 = $38.25
Cost per year $38.25 × 12 = $459
With the 800 W replacement 120 kWh and $20.40 a month; it saves $214.20 a year and pays for itself in about 11 months

Common questions

Where do I find the power of my appliance?

Look at the rating label or the manual: it is given in watts (W) or kilowatts (kW). If only amps and volts are given, multiply them to get watts.

Where do I find my electricity price?

On your bill, as the price per kilowatt-hour (kWh). The default is only a placeholder, so replace it with the usage rate on your bill. Fixed monthly charges are not included.

Why can the real cost be lower than the result?

The calculator treats the rated power as constant while the device is on. Many appliances, such as fridges, heaters with thermostats and washing machines, cycle on and off or draw less than their rating, so the real use can be lower.

What is the water, fuel, other mode for?

For anything that is used up by the unit: litres of water, gallons of fuel, washing cycles. Enter how much is used each time, how many times a month and the price per unit, and you get the cost per month and per year.

Other ways to ask what it costs you

What a price increase costs you How much a price rise costs per month, per year and over the years ahead. Open calculator → When does it pay off How long a one-off purchase takes to earn back its price through lower running costs. Open calculator → Cost per unit and per use Big pack or small, buy or subscribe — which is cheaper once you divide it out. Open calculator →

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