How it is calculated
Energy in kilowatt-hours is power in watts × hours of use ÷ 1,000. Multiplying by the number of days gives the monthly use, and multiplying by your price per kWh gives the cost. Use the full price from your bill, including transfer and taxes, for a realistic result.
Formula
kWh per day = power (W) × hours ÷ 1,000Cost per month = kWh per day × days × price per kWhExample
A 2 kW kettle used for one hour a day uses 60 kWh a month. At 0.25 € per kWh that is 15 € a month, or 180 € a year.
Tips from practice
- Heaters and saunas run at full power only part of the time; the thermostat switches them on and off.
- With a spot-price contract, running heavy appliances at night can cut the cost noticeably.
- The power is printed on the appliance label in watts (W) or kilowatts (kW).
Questions and answers
How much does a sauna cost per session?
A 6 kW heater used for about 1.5 hours uses roughly 6–9 kWh, depending on how long the thermostat keeps it on.
What price should I enter?
Divide the total of your last bill by the kWh used. That includes energy, transfer and taxes.
How do I find the power of an appliance?
Look at the label on the back or bottom, or in the manual. 1 kW = 1,000 W.
Found a mistake in a formula? Write to contact@planicalc.com