Cost to run a desktop computer
A desktop computer drawing 140 W costs 3.68p for each hour of running at 26.32p/kWh. Used 4 hours a day, every day, that comes to £4.74 a month.
An hour of running costs
3.68p an hour
That is 0.14 kWh. Used as set, it comes to £4.74 a month and £56.87 a year.
On the label or in the manual.
Standby, thermostats and off-peak use
A thermostat switches it on and off to hold a temperature. 100% if it runs flat out.
Drawn while plugged in and not running.
| Period | Cost | Energy | CO2e |
|---|---|---|---|
| An hour of running | 3.68p | 0.14 kWh | 30 g |
| A day, on average | 15.6p | 0.59 kWh | 129 g |
| A month | £4.74 | 18.0 kWh | 3.9 kg |
| A year | £56.87 | 216 kWh | 47 kg |
How we calculated this
Energy is power multiplied by time: 140 W running for an hour uses 0.14 kWh.
Standby is counted for every hour it is plugged in and not running, on days it is used and days it is not.
The typical figure is the average rating Centre for Sustainable Energy gives for a desktop computer. The low figure is Virginia Tech’s rating for the computer alone while awake, and the high figure adds its rating for a monitor, as Virginia Tech does in its own worked example. A gaming PC draws far more than any of these. The standby figure is what an ENERGY STAR certified desktop draws asleep, at the median.
The starting use for a desktop computer, 4 hours a day, every day, is where the calculator starts, not a measurement of your home: change it to how you use yours. A day is the average across the week, and a month is a twelfth of a 365-day year.
Electricity costs 26.32p/kWh. That is the published figure for the United Kingdom, 1 Oct – 31 Dec 2026, from Ofgem. Average for England, Scotland and Wales, paying by Direct Debit. No VAT on electricity from 1 October 2026 to 31 March 2027.
Standing charges are left out: you pay them whether or not the appliance runs.
Emissions use 0.217 kg CO2e per kWh, the lifecycle intensity of electricity generated in the United Kingdom in 2025, from Ember, via Our World in Data. Lifecycle means building the power stations and supplying their fuel are counted too. It is the grid’s average, not the particular power station an extra appliance brings on.
What drives the cost
A desktop computer draws 140 W while it is awake, and how much that adds up to depends almost entirely on how long it is left on. At 4 hours a day, every day, a desktop computer costs £56.87 a year, and a computer left on all day costs several times that.
Also called: PC, desktop PC, computer.
What it costs in the UK, Europe and the US
For a desktop computer used as typical (4 hours a day, every day), at each country’s published average electricity price.
| Country | Electricity price | An hour |
|---|---|---|
| United Kingdom | 26.32p/kWh | 3.68p |
| United States (average) | 18.19¢/kWh | 2.55¢ |
| Ireland | €0.4042/kWh | €0.057 |
| Germany | 0,3869 €/kWh | 0,054 € |
| France | 0,2561 €/kWh | 0,036 € |
| Spain | 0,2669 €/kWh | 0,037 € |
| Italy | 0,2966 €/kWh | 0,042 € |
| Netherlands | € 0,2558/kWh | € 0,036 |
Compared with similar appliances
| Appliance | Typical power | An hour | A year, typical use |
|---|---|---|---|
| Desktop computer | 140 W | 3.68p | £56.87 |
| Computer monitor | 14.2 W | 0.37p | £7.23 |
| Laptop | 50 W | 1.32p | £25.11 |
| Wi-Fi router | 10 W | 0.26p | £23.06 |
| Games console | 120 W | 3.16p | £23.06 |
How to spend less on it
- Let it sleep, or switch it off, when you step away: asleep, the median certified desktop draws only 1.6 W.
- Turn the monitor off separately if you leave the computer running for a download: the screen is a large share of what the whole set draws.
- A laptop draws far less for the same work, if you are choosing what to buy.
Questions
How much does a desktop computer cost to run per hour?
At 26.32p/kWh, a desktop computer drawing 140 W costs 3.68p for every hour of running at full power.
How much does a desktop computer cost to run a year?
Used 4 hours a day, every day, it costs about £56.87 a year at 26.32p/kWh, or £4.74 a month.
How many watts does a desktop computer use?
Most draw between 120 W and 270 W while running, and 140 W is typical. The rating is on the label or in the manual.
How much does a desktop draw when it is idle?
ENERGY STAR measured a median of 10.6 W for certified desktops sitting idle with the display on, and 1.6 W asleep. That is well below the 140 W typical rating here, which reflects a desktop working; a machine doing heavy work, or a gaming PC, draws several times more.
Sources
- How much electricity am I using?, Centre for Sustainable Energy, July 2026. “Desktop computer (140 W)”
- ENERGY SERIES: Estimating Appliance and Home Electronic Energy Use, Virginia Cooperative Extension, Virginia Tech, 26 February 2020. “Personal computer CPU - awake / asleep = 120/30 or less”
- ENERGY SERIES: Estimating Appliance and Home Electronic Energy Use, Virginia Cooperative Extension, Virginia Tech, 26 February 2020. “Monitor - awake/asleep = 150/30 or less”
- ENERGY STAR Certified Computers V9.0 (open data), ENERGY STAR, US Environmental Protection Agency, 26 September 2026. “ENERGY STAR certified desktop computers, sleep-mode power: median 1.6 W across 293 certified models, 10th to 90th percentile 0.8 W to 3.2 W (models where type='Desktop').”
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