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Computer electricity use

Estimate desktop or laptop running cost from average power, workload and hours of use.

✓ Adjustable load✓ Monthly consumption✓ Annual cost

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Power, load and usage

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Indicative diagram of this calculator inputs — Cost depends on real power draw, usage time and the price per kWh.

How we calculate consumption

We apply the average load factor to the entered power, multiply by hours and days, then convert the result into kWh and euros.

W ÷ 1000 × hours × load × days × €/kWh

The PSU rating is not real consumption

A 750 W power supply can support high peaks, but the computer usually draws much less. For better accuracy, use a plug-in power meter.

Workload matters

A dedicated GPU under a demanding game can dominate power use. At idle, during browsing or video playback, demand is usually much lower.

Use real system power, not the PSU rating

A computer power supply rated at 650 W or 750 W is designed to support a possible load; it does not mean the PC consumes that amount continuously. Real demand changes with CPU and GPU activity, power limits, display output and workload.

Split heavy and light-use hours

Gaming, rendering and other GPU-heavy work can use far more electricity than browsing, office work or video playback. If your day includes both, a single average load percentage is only an approximation. For better accuracy, calculate the periods separately or measure the complete PC at the wall.

Remember the rest of the setup

The calculator covers the computer itself unless you deliberately include other loads. Monitors, speakers, routers, external drives and charging devices can be estimated separately and then added to the total.

For more context, read computer electricity use and the guide on measuring appliance consumption.

Editorial review: 11 Oct 2026. A socket power meter gives a better average than the PSU nameplate rating.