The Desktop That Never Sleeps: What 24/7 Really Adds to Your UK Energy Bill
Photo: U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office, Public domain, via Wikimedia Commons
There is a familiar office ritual: the last person leaves, the lights go off, and the desktop under the desk keeps humming away because nobody wants to be the one who shuts it down. Sometimes that is justified. Often it is just habit. The useful question is not whether leaving a PC on is bad, but what it actually costs in your space, on your tariff, with your machine.
Measure at the wall, not the label
The power supply label tells you the maximum it can deliver, not what the PC is drawing. A 750W PSU in a gaming rig may pull 50W at the Windows desktop and 350W in a game. A business mini-PC may idle at 8W and never see 60W. You need a plug-in energy monitor for half an hour, not a guess based on the PSU badge.
Measure four states: switched off at the wall, sleep or standby, idle at the desktop, and load. For load, run the programs you actually use — a game, a CAD preview, a big spreadsheet recalculation — rather than a synthetic benchmark that makes the fans scream. Note the wattage for each state and how long the machine spends there on a normal day.
The maths, without the doom
Electricity is billed in kilowatt-hours. A 10W device running 24/7 for a year uses about 87.6 kWh. At an illustrative 28p per kWh, that is roughly £24.50. A desktop idling at 55W for the same period uses about 481.8 kWh, or around £135. A machine in sleep at 3W costs about £7.35. A proper workstation sitting at 100W around the clock would be nearer £245.
Those numbers are not a scare story. They are a reason to measure. A small office with five desktops idling at 40W each is looking at roughly £490 a year at 28p, before anyone opens a browser. A single gaming PC left on for convenience is a smaller issue, but it is still money for nothing. Check your own unit rate and standing charge; the 28p figure is only a working example.
PSU efficiency is not a magic wand
An 80 Plus rating tells you something about efficiency at 20%, 50%, and 100% load. It does not promise miracles at 10W. A big PSU idling at 50W may be running well below its efficient band, while a smaller, decent-quality unit could do better. That said, replacing a working PSU purely to cut idle draw rarely pays back quickly. If you are building fresh, size the PSU for the load you expect, not for a fantasy upgrade three years away.
Windows settings that actually matter
Sleep is the obvious first step, but check what is stopping it. Windows power settings can be defeated by a background app, a USB device, a network adapter, or a wake timer. Run powercfg /requests from an elevated command prompt to see what is holding the machine awake. Then look at the power plan and decide whether sleep, hibernate, or a scheduled shutdown fits the way people work.
Fast Startup is not the same as sleep. It is a hybrid shutdown that can make booting feel quicker, but it can also complicate dual-boot setups and some driver updates. Hibernate writes memory to disk and uses no power while off, which is useful if you want to resume work after a power cut. For a desktop that needs to be reachable, sleep plus wake-on-LAN is often the better compromise.
Wake-on-LAN and the small-office trade-off
Wake-on-LAN lets another device send a magic packet to start the PC. It is genuinely useful for remote access, overnight backups, and patch management. But it requires standby power at the network card, a BIOS setting that may conflict with deep sleep or ErP mode, and a router or management tool that can send the packet. It is not automatic, and it is not free.
A mini-PC or laptop often makes more sense for a small office that needs an always-available machine. They tend to idle lower than a gaming tower, and they take up less space. If the job is file sharing, remote desktop, or a line-of-business app, a low-power box left on deliberately is easier to justify than a full-size desktop idling with RGB lighting on.
When leaving it on is genuinely justified
Some machines should stay on. A backup server that runs overnight, a CCTV recorder, a remote-access PC, a machine processing long jobs, or a system that must receive updates outside office hours all have a reason. The point is to make that reason explicit. If nobody can explain why the PC is on at 2am, it probably does not need to be.
For gamers, the usual culprit is convenience: the PC stays on because booting takes a minute and the launcher is already open. Sleep handles that. For small offices, the culprit is often a shared folder or a remote worker who occasionally connects. A scheduled wake time, a wake-on-LAN setup, or a tiny always-on machine can solve that without leaving every desktop running.
A sensible UK office policy
Measure the actual draw, set sleep for idle periods, schedule updates and backups, and document the exceptions. Check that wake timers are doing what you think they are doing. If you have a UPS, remember that it is there to ride out short outages, not to keep a room of idling PCs alive for an hour.
The 24/7 PC is not a myth, and it is not automatically a disaster. It is a choice with a meter attached. Once you know the wattage and the unit rate, the decision gets a lot less emotional and a lot more sensible.
