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CALCPARK

Electricity Cost Calculator

What any appliance costs to run from its watts (or kW, or amps × volts), hours of use and your price per kWh – per day, month and year, for several devices at once.

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How to use it

  1. Enter the unit price from your electricity bill (price per kWh) and, if you like, a currency label.
  2. For each appliance enter the power – in watts, kilowatts, or amps plus mains voltage – and the hours it runs per day.
  3. Adjust days per week for things you do not use daily (washing machine, tumble dryer) and add the standby wattage if it stays plugged in.
  4. Add more appliances to compare them; the table lists each one’s kWh per day and cost per month and year.
  5. Read the daily, monthly and yearly totals, then copy the summary or share the link.

Example

A 150 W fridge compressor that runs about 8 hours a day: 150 × 8 ÷ 1,000 = 1.2 kWh a day, 438 kWh a year; at 0.30 per kWh that is 131.40 a year. A 2 kW fan heater used 3 hours a day uses 6 kWh a day and costs 1.80 a day or 657.00 a year. Together: 7.2 kWh a day, 2.16 a day, 65.70 a month, 788.40 a year.

Formulas and assumptions

watts = W | kW × 1,000 | amps × volts
kWh per day = (watts × hours on + standby W × (24 − hours on)) ÷ 1,000 × days per week ÷ 7
              (+ standby × 24 h on the days it is not used)
cost per day = kWh per day × price per kWh
month = 365 ÷ 12 = 30.42 days;   year = 365 days

Amps × volts gives apparent power (VA); for heaters, lamps and most electronics with power-factor correction it equals the real wattage, while motors can draw up to 10–20% less real power than VA. The result assumes the appliance draws its rated power for the whole time it is on; thermostat-controlled devices (fridges, ovens, irons) draw their rating only while heating or cooling, so enter the compressor/heating duty hours or the energy-label kWh instead. Standing charges, tiered tariffs and time-of-use rates are not modelled – enter an average unit price.

Sources: US Department of Energy – Estimating appliance and home electronic energy use, European Commission – Energy label.

Questions

Where do I find the wattage?
On the rating plate (usually on the back or underneath), in the manual, or on the energy label. If only amps are given, choose "Amps × volts" and enter your mains voltage – 230 V in Europe, the UK, Australia and most of Asia; 120 V in North America.
Why is a month 30.42 days?
So that twelve months add up to exactly one 365-day year. A calendar month ranges from 28 to 31 days, so a real bill will differ by a few percent either way.
How much does standby really cost?
Each watt of standby costs 8.76 kWh a year. A home with 30 W of standby across TV, consoles, chargers and routers uses 263 kWh a year – 78.84 at 0.30 per kWh.