To calculate the electricity costs of an appliance you need only three figures: its power, its operating time and the price per kilowatt hour. With these three quantities you can work out the monthly amount for every device, from the kettle to a standby unit. This guide shows the steps, uses a sourced example price and marks every assumption clearly.
Short answer: The electricity costs of a device result from power in kilowatts times operating hours times the price per kilowatt hour. As an example price, the BDEW electricity price analysis of October 2026 gives 37.3 cent per kWh for an annual consumption of 3,500 kWh. A 100-watt device that runs three hours a day therefore costs about 3.36 euro per month. Last updated: November 2026.
The most important points in brief
- The formula is: power in kW times hours per day times days times price per kWh.
- You find the power on the rating plate or the energy label, usually in watts.
- The example price comes from the BDEW analysis at 37.3 cent per kWh. Your own tariff may differ.
- Standby devices cost little per hour but add up noticeably over a year.
- The results are worked examples. Your supplier’s bill is the binding figure.
Which formula do you need?
The basic formula is simple. You multiply the power in kilowatts by the operating hours, which gives the energy used in kilowatt hours. You then multiply this figure by the price per kilowatt hour. The result is the amount the device costs in that time.
Formula: Costs per month = power in kW × hours per day × 30 days × price per kWh. To convert watts into kilowatts, divide by 1,000. A device with 2,000 watts therefore has a power of 2 kW.
Where does the electricity price come from?
You find the price per kilowatt hour on your electricity bill or in your contract. As a guide value, the BDEW electricity price analysis of October 2026 gives an average price of 37.3 cent per kWh for an annual consumption of 3,500 kWh. The association’s analysis refers to new-customer tariffs as of 1 October 2026.
On your bill you find the working price per kWh and, where applicable, a basic price that is due regardless of consumption. The total price is made up of procurement and sales, grid fees, and taxes, levies and surcharges. For the bill of a single appliance you only need the total price per kWh. Looking at the breakdown helps if you want to understand where the amount comes from.
A worked example step by step
Assumption: According to the rating plate, a television has a power of 100 watts and runs for three hours on 30 days. The price is 0.373 euro per kWh. The calculation runs in four steps.
- Convert the power: 100 watts are 0.1 kW.
- Work out the operating hours per month: 3 hours a day times 30 days gives 90 hours.
- Calculate the energy: 0.1 kW times 90 hours gives 9 kWh per month.
- Calculate the costs: 9 kWh times 0.373 euro gives about 3.36 euro per month.
Extrapolated to the year, this example gives about 40 euro. The calculation applies only to the assumed use and power. If one of the three quantities changes, the result changes accordingly.
Typical appliances compared
The table below works through several appliances with the same assumptions. Power and operating time are example assumptions for typical appliances. A 2018 brochure of the Verbraucherzentrale NRW (status 05/2018) served only as a rough guide, and appliance power ratings have changed since. Read the power of your own appliance from its rating plate or energy label and adapt the operating time to your daily routine.
| Appliance | Power (assumption) | Use (assumption) | kWh per month | Costs per month at 0.373 euro per kWh |
|---|---|---|---|---|
| Kettle | 2 kW | 30 minutes a day | 30 | about 11.19 euro |
| Television | 100 W | 3 hours a day | 9 | about 3.36 euro |
| Standby device | 3 W | 24 hours a day | 2.16 | about 0.81 euro |
| Laptop with charger | 60 W | 4 hours a day | 7.2 | about 2.69 euro |
All values in the table are assumptions. For a more precise result, read the power from the rating plate or measure consumption with a plug-in energy meter.
What do the results mean in everyday life?
The results show that short use of a powerful device and long use of a weak device have very different effects. A kettle draws a lot of power but runs only briefly. A standby device draws little but runs constantly. That is exactly why the calculation helps to set the right priorities.
If you calculate several devices, you add up the monthly amounts. This gives a realistic estimate of your total consumption. The sum is not a guarantee, but it shows the order of magnitude in which your electricity costs move.
Which mistakes often happen in the calculation?
The most common mistake is confusing watts with kilowatt hours. A watt is a power, while kilowatt hours are an amount of energy. Only when you multiply the power by the time do you get the quantity that the meter records and your bill prices.
A second mistake is overestimating operating hours. A device that feels as if it runs all the time often runs only briefly. A third mistake is forgetting devices that draw power in the background, such as routers or chargers. A short list of all sockets helps to close this gap.
What does this come to over a year?
For annual costs you multiply the monthly amount by twelve. For the kettle from the table, 30 kWh per month comes to about 360 kWh per year, which at 0.373 euro per kWh is about 134.28 euro. This figure is a model calculation based on the assumed use and not a measured value.
Frequently asked questions
Where do I find the power of a device?
The power is usually on the rating plate, often on the back or on the power adapter. The EU energy label additionally gives figures on consumption, which are suitable for comparison.
Which price should I use?
The most accurate figure is the price from your own contract. The value from the BDEW analysis is an average for an example consumption. It is useful for a rough estimate, but it is not binding for your bill.
How accurate is the calculation?
The calculation is only as accurate as its assumptions. The power on the rating plate is often a nominal value, and actual consumption can differ from it. If you want more precision, measure over several days with a power meter. For a first estimate, the simple calculation is usually sufficient, and the deviation usually stays manageable.
Does the formula also work for heating appliances?
The formula applies to any electrical device as long as you know its power and operating time. For heaters with changing operation, the result depends strongly on use, so the assumptions matter especially there.
How to proceed now
- List your largest appliances and note the power from each rating plate.
- Estimate the daily operating time and check it against a typical day.
- Calculate with your own electricity price from the contract rather than the example value.
- Add up the monthly amounts and compare them with your annual statement.
Related guides
- Climate, energy and costs 2027: The overview for tenants and students
- Power guzzlers at home: Which appliances use a lot of power
- Grid fees 2027: What the reduced subsidy means for electricity
- Saving Electricity as a Student: Energy and Utility Costs
Sources: BDEW electricity price analysis, status October 2026 (in German) and Verbraucherzentrale NRW: Strom sparen, Spartipps, brochure, status 05/2018 (in German).
Last updated: November 2026. This guide is general information, not individual advice.
