To estimate a gaming PC’s electricity cost, you need its real power draw, the time spent at that load and your electricity unit rate. The calculation is: watts × hours ÷ 1,000 = kWh; kWh × price per kWh = cost.
Do not use the power supply’s wattage as the PC’s consumption. A 750W PSU is a capacity, not a claim that the machine constantly draws 750 watts. Measure at the wall for the most useful answer.
1. The quick UK running-cost calculation
This worked example uses 26.11p per kWh, Ofgem’s Great Britain average electricity unit rate for a standard-variable tariff paid by Direct Debit from 1 July to 30 September 2026. It is a dated illustration, not your personal tariff. Enter the unit rate printed on your bill for an accurate result.
| Measured average | Use | Energy each month | Monthly cost | Annual cost |
|---|---|---|---|---|
| 80W | 4 hours a day | 9.7 kWh | £2.54 | £30.50 |
| 300W | 4 hours a day | 36.5 kWh | £9.53 | £114.36 |
| 500W | 4 hours a day | 60.8 kWh | £15.88 | £190.60 |
For the middle row: 300 × 4 × 365 ÷ 1,000 = 438 kWh a year. Then 438 × £0.2611 = £114.36. Replace 300W, four hours and 26.11p with your own measurements. If you game only on certain days, use the actual number of days rather than automatically multiplying by 365.
2. Separate idle, gaming and heavy workloads
A PC does not have one permanent wattage. It may sit near idle while you read or stream, rise during a game, and behave differently again while rendering, compiling or running a sustained CPU-and-GPU workload. The honest estimate divides your week into those periods.
- Measure 30 minutes of ordinary desktop or streaming use.
- Measure several representative games rather than one loading screen or menu.
- Measure any genuinely regular heavy workload separately.
- Multiply each average by its own hours, then add the kWh totals.
Menus with uncapped frame rates, loading transitions and short boost spikes can distort a snapshot. A longer average is more useful than the highest number the monitor flashes. The monitor, speakers and other peripherals also consume power, so decide whether your measurement is for the tower alone or the whole desk and label it accordingly.
3. Measure at the wall
A plug-in energy monitor between the wall socket and the PC’s power lead gives the clearest household-cost measurement because it captures the machine’s input power, including conversion losses. Reset its accumulated-energy reading, use the PC normally for several days, then divide the recorded kWh by the measured days.
Use a suitable, undamaged monitor and follow its instructions. Do not overload an adaptor or daisy-chain extension leads. Electrical Safety First’s extension-lead guidance is a sensible safety reference if the desk already has several connected devices.
Software figures from a GPU or CPU utility can help compare settings, but they usually measure selected components rather than everything taken from the wall. They are diagnostic clues, not a complete electricity-bill reading.
4. Use the right tariff figure
For England, Scotland and Wales, take the electricity unit price from your latest bill or supplier account. Ofgem’s price-cap rate page explains that rates vary by region, payment method and meter type, while fixed tariffs can differ from the cap. Northern Ireland has a separate energy market and consumers should use their supplier rate and current Utility Regulator information.
The daily standing charge is normally paid for having the electricity supply, whether the gaming PC is on or off. It therefore should not be added as though the PC alone created it when calculating the incremental cost of gaming. Include it only if you are modelling the household bill as a whole.
Time-of-use tariffs need separate peak and off-peak calculations. Multiply the kWh used in each period by that period’s rate, then add the two costs. The same applies to a discounted weekend or smart tariff.
5. What actually changes the total?
Power limits, frame-rate caps, display resolution, game settings, CPU and GPU utilisation, monitor choice and time played can all affect the result. A faster graphics card is not automatically more expensive for every task: if it completes capped work efficiently, the measured difference may be smaller than its maximum board-power figures suggest. Measure the complete use pattern instead of inferring a bill from one specification.
| Question | Useful evidence | Misleading shortcut |
|---|---|---|
| What does my present PC cost? | Several days of accumulated kWh at the wall | Reading the PSU label |
| Did a setting save energy? | Repeat the same scene and duration before and after | Comparing two unrelated games |
| What will an upgrade cost? | Comparable independent whole-system tests plus your hours and tariff | Adding CPU and GPU maximum figures |
| What does the whole desk cost? | Measure the tower, display and peripherals together | Calling a component-only reading the total |
6. Reduce cost without spoiling the experience
Start with changes you can measure and reverse: use a sensible frame-rate cap, let the display and PC sleep when genuinely idle, close unwanted background workloads, and test a supported GPU power limit or efficiency setting carefully. Microsoft documents the current Windows 11 power settings; avoid copying an aggressive plan that creates instability or poor performance.
Maintenance can matter too. Blocked airflow may increase fan noise and temperature, while unstable tuning can waste time even if its wattage looks impressive. Change one variable at a time and keep the setting only if performance, stability and power all remain acceptable.
7. Put energy cost in the upgrade decision
Electricity is one part of an upgrade, not the only part. Price, performance, reliability, noise, available connectors and whether the existing power supply remains suitable all matter. Browse GPUsed’s current graphics-card stock for real product choices, or start with the buying guide if you are still deciding.
If an upgrade displaces a working unit, GPUsed can also quote for selected hardware. Use the power-supply selling page for a PSU or the wider selling route linked from the site; submit the exact model and condition rather than an estimated wattage alone.
Sources, assumptions and review date
Rates and guidance checked on 12 September 2026. The 26.11p example is Ofgem’s published Great Britain average for a specific cap period and payment method; it will age. Your supplier’s current unit rate and a representative wall measurement remain authoritative for your calculation.