What this electricity cost calculator does
Enter a device's power draw in watts and its running time — or its yearly consumption in kilowatt-hours: the calculator shows the electricity cost per hour of use, per day, month and year. Standby consumption appears as its own line, including its share of the total. Everything is calculated locally in your browser.
How do I calculate what a device costs to run?
Two steps are enough: kilowatt-hours = watts × hours ÷ 1,000, then cost = kilowatt-hours × unit rate. A 2,000-watt fan heater running two hours a day uses 4 kWh — at 37 cents per kilowatt-hour that is 1.48 € a day, about 45 € a month and a good 540 € a year. If a device only runs on some days of the week, the calculator spreads the running time across the whole year as an average.
What does standby cost per year?
More than the small wattage numbers suggest: a single watt of continuous draw is 8.76 kWh a year, because a year has 8,760 hours. The calculator counts standby towards the total but also lists it separately — with its own cost and its share of the yearly consumption. It is only applied to the hours the device is not running. With the preset price of 37 cents per kilowatt-hour this works out to:
| Continuous draw | Consumption per year | Cost per year |
|---|---|---|
| 1 W | 8.76 kWh | 3.24 € |
| 2 W | 17.52 kWh | 6.48 € |
| 5 W | 43.80 kWh | 16.21 € |
| 10 W | 87.60 kWh | 32.41 € |
Watts or kilowatt-hours — which input path fits?
You find the wattage on the rating plate, in the manual or on a plug-in power meter; you estimate the running time and days per week yourself. The yearly kWh figure is on the energy label, or you can extrapolate it from a week of metering. Important: a yearly figure already includes standby — on that path the calculator deliberately does not add it again. If you have no numbers at hand, click one of the sample devices in the calculator — from fridge to router. Those are ballpark figures for orientation, not measurements.
What does a kilowatt-hour of electricity cost in Germany?
According to the BDEW electricity price analysis (as of April 2026), the German household electricity price in 2026 so far averages 37.0 cents per kilowatt-hour — including, among other components, network charges (9.3 ct on average) and taxes, levies and surcharges (12.6 ct). This average is the calculator's preset. Your tariff will differ, so enter the unit rate from your own bill.
Day, month and year — how does the conversion work?
The calculator uses 365 days and twelve months; the monthly value is one twelfth of the yearly one. Leap years are ignored, which introduces an error of 0.27 percent. The cost per hour of use refers only to the hours the device is actually running — not to every hour of the day.
What the calculator deliberately leaves out
- The monthly standing charge of your tariff: it accrues regardless of the device and would distort every per-device figure. Only the unit rate is used.
- Cycling devices such as fridges or heaters actually run for less time than they are switched on — enter the compressor's real runtime there, not the time plugged in.
- Dynamic or time-of-use tariffs: the maths use one fixed price per kilowatt-hour.
Privacy
Your inputs never leave your device — the calculation is a handful of multiplications right in the browser. Data is stored only locally on your device, so the tool reopens where you left off. The address bar carries the entered numbers so you can share a result as a link — no server is involved in that either.