At the Ofgem cap rate for 1 October to 31 December 2026, a desktop PC rated 200W costs about 42.1p a use and £153.71 a year when 8 hours a time, once a day.
| Per hour of running | 5.3p |
|---|---|
| Per use | 42.1p |
| Per day | 42.1p |
| Per year | £153.71 (584 kWh) |
Calculated at 26.32p per kWh, the capped electricity unit rate for 1 October to 31 December 2026 on a standard variable tariff paid by direct debit. Electricity carries no VAT in that period, so this is the full unit price. The 54.83p daily standing charge is not included, because you pay that whether or not anything is switched on.
Two things worth knowing about that figure. The cap limits the unit rate, not your bill, so using more still costs more. And it is a Great Britain average: the actual capped rate is set per region, so your own rate could move these numbers either way. It is on your bill.
Desktop PC has no thermostat cycling it on and off, so the running cost is simply the rated power multiplied by the time it is switched on. Short bursts of high wattage cost less than people expect.
Figures for desktop pc run from about 60W to 600W. The power supply rating is not the draw. A machine with a 750W supply might pull 60W browsing and 400W under load. Office work sits at the low end; gaming and video rendering sit at the high end, and a dedicated graphics card is usually the largest single component.
Let it sleep rather than run a screensaver, which keeps the machine at full power. A monitor left on overnight costs more than most people expect.
Reading the power supply wattage as the running cost. It is a maximum, not a measurement.
Annual running cost against the appliances closest to it, on the same assumptions. The ordering surprises people: short bursts of very high wattage usually cost less than something modest left on for hours.
| Appliance | Per year |
|---|---|
| Electric heater | £189.50 |
| Desktop PC | £153.71 |
| Tumble dryer | £144.10 |
| Dishwasher | £121.05 |
| Fridge freezer | £103.75 |
Across a year, a desktop PC on these assumptions is about 23.4% of a typical annual electricity bill of £658.00 at these rates.
The figures here use the capped rate. If you are on a fixed tariff, or you want to add several appliances together, put your own unit rate into the energy cost calculator on the homepage.