What you need to know
- Idle, office work, gaming and rendering can have very different power draw.
- Measure at the socket for the best result.
- Include monitor and peripherals separately when they matter.
Use your own measurements
Use the linked BricoDato resource to check these inputs in your own situation. The power-supply rating is a capacity ceiling, not the electricity bill.
Do not use PSU wattage as consumption
A 750 W power supply does not mean the PC constantly uses 750 W. It only describes the supply’s output capability.
Workload changes everything
A dedicated GPU under gaming or rendering can dominate system power. Browsing, video playback and idle periods are usually much lower.
Measure representative sessions
If possible, record power during light use and gaming separately, then multiply each by its own hours rather than using one rough average.
Remember the rest of the setup
Monitors, speakers, network equipment and chargers can add meaningful energy over long daily sessions.
Calculate a gaming or working PC as a whole system
The power-supply rating is a capacity ceiling, not the electricity bill. PC energy depends on CPU and GPU workload, monitor brightness, peripherals and how long the computer is truly active.
Example to adapt
Assume a desktop and monitor together average 250 W during four hours of gaming each day. Energy is 0.25 × 4 = 1 kWh daily, or 30 kWh in 30 days. At a sample €0.20/kWh this costs €6. If the actual combined average is 400 W instead, the monthly estimate becomes 48 kWh, or €9.60.
| Average combined draw | 4-hour session | 30 sessions |
|---|---|---|
| 100 W | 0.4 kWh | 12 kWh |
| 250 W | 1.0 kWh | 30 kWh |
| 400 W | 1.6 kWh | 48 kWh |
Checks before acting
- Measure computer and monitor consumption separately or together without counting either twice.
- Compare representative idle, office, game and sleep sessions.
- Use the average kWh over a full session rather than the highest instantaneous reading.
- Check automatic sleep settings, frame-rate limiting and peripherals before buying new hardware solely for efficiency.
Final check
Do not treat the wattage printed on a PC power supply as its continuous consumption. A 750 W PSU indicates a capacity limit, not what the complete computer draws while idle, browsing or gaming. Measure the computer and monitor over representative sessions, recording how long each type of activity lasts and whether the GPU is heavily loaded.
- Measure wall-socket power when possible.
- Separate heavy and light workloads.
- Add display consumption separately.
- Use real daily hours rather than maximum possible use.
Keep a small job sheet
Note workload, wall-plug kWh, monitor status, run time and any power-limit settings.
Turn the guide into a decision
Calculate monthly kWh from measured sessions rather than a single maximum-power estimate. For gaming, record a few typical hours and include the monitor and speakers if they are relevant; power-limiting or display settings should be checked against actual performance and stability.