Electricity Cost Calculator
Find out what any device costs to run. Enter wattage, daily usage hours, days per week and your electricity tariff to get daily, monthly and yearly cost instantly.
Last updated: May 2026
Enter power and usage to calculate electricity cost.
Cost/day = (W / 1000) * hours * tariff
What does it actually cost to run your devices?
The formula is straightforward: divide wattage by 1,000 to get kilowatt-hours per hour, then multiply by usage time and your tariff. A 100 W television running 5 hours a day at €0.32/kWh costs €0.16 per day, or about €4.80 per month. That feels minor until you stack 10 devices together.
The days-per-week input matters more than most people expect. A washing machine used twice a week costs less than a quarter of what daily use would cost, even at the same cycle wattage.
Common appliance running costs
Monthly cost at €0.32/kWh. Refrigerator and NAS run continuously (24 h/day). All others at 4 h/day, 7 days/week.
| Appliance | Wattage | Monthly cost |
|---|---|---|
| LED bulb | 8 W | €0.31 |
| Laptop | 45 W | €1.75 |
| NAS / home server (24 h/day) | 30 W | €7.00 |
| Television | 100 W | €3.89 |
| Refrigerator A++ (24 h/day) | 120 W | €27.99 |
| Gaming PC | 500 W | €19.48 |
| Air fryer 1.5 kW | 1500 W | €58.45 |
| Electric kettle | 2000 W | €77.93 |
| EV home charger 7.4 kW | 7400 W | €288.38 |
Frequently Asked Questions
My bill shows kWh but my device shows W. How do I convert?
Watts measure power (rate of energy use). Kilowatt-hours measure energy (total consumption over time). To convert: multiply the device wattage by the number of hours it runs, then divide by 1,000. A 500 W gaming PC running for 4 hours uses 500 * 4 / 1,000 = 2 kWh. Multiply that by your tariff to get the cost for that session.
Why does the calculator give a higher number than my actual bill?
Several things reduce real-world consumption below the calculator estimate. Many devices do not run at rated wattage continuously. A gaming PC draws 500 W under full load but only 80-120 W at desktop idle. Devices in standby still draw power (1-5 W each), but far less than active use. If multiple people share a meter, the bill reflects the household total, not one device. The calculator assumes constant draw at the wattage you enter, so it gives a useful upper bound rather than a precise figure.
How do I find out my actual electricity tariff?
Check your most recent electricity bill. The per-kWh price is usually listed under "energy charges" or "usage rate." Your supplier's online portal or app also shows the current rate. If you have a smart meter, the in-home display or its companion app often shows real-time cost per kWh. In the Netherlands, the tariff appears on your jaarafrekening or maandelijkse overzicht. Note that some contracts have peak and off-peak rates; use the rate that applies to when you run the device most.
Does it cost more to run a device at full power or part power?
For most devices, energy cost scales roughly linearly with power draw; half the wattage means half the cost per hour. However, some devices are less efficient at very low loads. Variable-speed motors (heat pumps, inverter air conditioners) are most efficient in a mid-range band. Switching power supplies (laptop chargers, LED drivers) can be slightly less efficient at 5-10% load versus 50-80% load. For practical home energy calculations, treating cost as linear with wattage is accurate enough.
Next step in this workflow
Know the load: now size the cable for the circuit.