How much does it cost to run a desktop PC and monitor per hour in the UK?

Entertainment By Marcus BellPublished 21 October 2026

What a desktop and monitor draw

A desktop computer is two appliances on the same desk, and the monitor is the one people forget. Each has its own published figure, and neither of them is the number on the power supply.

The computer side is best measured in real homes, because a tower's draw depends on what you ask of it. Researchers at Lawrence Berkeley National Laboratory in California metered desktops at the socket in ordinary households and found an average of 66.1 watts whenever they were on, with the monitor counted separately, and 2.0 watts on standby. Newer office machines do better at rest. The ENERGY STAR certification for Lenovo's ThinkCentre M70s Gen 5, a mainstream Intel office tower, records 28.2 watts idling at the desktop, 1.1 watts asleep and 0.7 watts off. Apple puts the M4 Mac mini at 4 watts idle and 65 watts at its absolute maximum.

Monitors are certified the same way, at a set brightness with an ordinary picture on screen. The figures for five common Dell office screens run from 10.6 watts for the 24 inch P2425H, through 12.7 watts for the 27 inch P2725H and 17.0 watts for the 27 inch 1440p U2724D, up to 27.2 watts for the 34 inch P3424WE ultrawide and 28.3 watts for the 27 inch 4K U2723QE.

We use 77 watts for the pair, the 66.1 watt home average plus a 10.6 watt 24 inch monitor. A new office tower doing email will sit below that, and a few years old machine with a second screen will sit above it.

Per hour and per working day

The year column counts 260 weekdays and makes no allowance for holidays, so most people working from home will land a little under it. The two idle rows are the floor for a modern machine with nothing running, and real work such as video calls lifts them towards the typical row.

Rates: Ofgem cap 1 October to 31 December 2026 at 26.32p per kWh (source), EIA residential average June 2026 at 18.34 cents per kWh (source). Checked 2026-09-22.

The screen choice matters more than people think

Going from a 24 inch 1080p monitor to a 27 inch 4K one adds about 18 watts, which is a quarter again on top of the whole typical setup. Over a year of weekdays that is £9.70 extra, and a second screen adds its own figure on top in the same way.

Brightness moves the number as well. The certified figures are measured at a set brightness, and a monitor turned up to its maximum for a bright room draws more than the label says, so turning it down to a comfortable level is a free saving on any screen you already own.

Leaving it on overnight and around the clock

The real cost of a desktop is the hours it spends switched on with nobody at it. An office tower idling at 28 watts through a 16 hour evening and night uses 0.45 kilowatt hours and costs 11.9p a night, which is £43.35 across a year. Put it to sleep instead and the same 16 hours at 1.1 watts cost 0.46p, or £1.69 a year. Switching off fully at 0.7 watts saves another 61p a year on top of sleep, which is rarely worth the slower start in the morning.

An older or busier machine left running all the time costs a good deal more. At the 66.1 watt home average with the monitor asleep, 24 hours a day for a year comes to £152. If you want something on around the clock for downloads or files, a small machine such as the Mac mini at 4 watts idle costs £9.22 a year, which is the whole case for a low power box over an old tower kept running in the corner.

Working from home, where the money actually goes

For a home worker the computer is rarely the expensive part of the day. A desktop and monitor cost 16p for eight hours, and the laptop alternative costs 6.7p. A 2kW oil filled radiator running half the time to keep a spare room warm costs £2.11 over the same eight hours, and even a 38 watt heated throw over your knees costs 8.0p, about half the cost of the computer.

Every watt the PC and monitor draw ends up as heat in the room, which is a small consolation in January and an annoyance in July. It is also why a laptop is the cheaper choice twice over in winter, since it costs less to run and lets you work in whichever room is already warm. Our guide to what a gaming PC uses per month covers the machines that do make a dent in the bill, which is anything with a large graphics card running a game.

What actually lowers the cost

• Set the computer to sleep after 15 or 20 minutes of inactivity, because the gap between 28 watts idle and 1 watt asleep is where almost all the saving is.
• Let the monitor sleep with the computer rather than leaving it on a screensaver, which keeps the backlight lit and the full on mode figure ticking.
• Pick the screen for the work. A 1080p or 1440p monitor is enough for documents and spreadsheets and draws between a third and three fifths of what the 27 inch 4K model does.
• Turn the brightness down to what is comfortable, which costs nothing and lowers the draw on any LCD.
• Switch the extension lead off at the end of the week if the desk also holds speakers, a printer and a docking station, since each one keeps a small standby draw going all weekend.
• Do not replace a working computer to save electricity. The gap between a typical desktop and a laptop is £24.64 a year of weekdays, so a new machine pays for itself on power alone only over many years.

What this costs in the United States

At the EIA residential average of 18.34 cents per kilowatt hour, a 77 watt desktop and monitor cost 11.3 cents for an eight hour day and about $2.45 for a month of weekdays. A laptop doing the same work costs about $1.02 a month.