Electricity Cost of Running a PC 24×7

I have a PC at home, which is permanently switched on. I’ve wondered just how much the PC costs to run, and I recently got the opportunity to find out. I’ve borroweed a Electricity Plug-In Power and Energy Monitor, which I’ve been evaluating. The monitor provides voltage, current and consumed power readings.

The monitor plugs into the wall power socket, and then has a 13 Amp socket to correct to the equipment. As the back of my PC is somewhat inaccessible, and all my equipment is run through a single socket I placed the power meter at the main power socket.

This is shown in the photograph, where the display is showing the current voltage reading, for the domestic UK power supply of 240V.

This was not conducted under proper test conditions, but gives and indication of the power consumption of the PC. For reference this is a 2200 AMD processor, with Nvidia 128MB graphics card, 2 x 160GB disc drives and 2 x optical drives. This would have been a typical reasonably powered machine about 2-3 years ago.

The amount of power consumed makes for quite interesting reading. The measurements are shown below:

The background current, which includes a USB Hub, Scanner, VCR and printer etc, was 0.17A
With monitor and PC plugged in, but powered off: 0.20A, so only 0.03A standby current when powered off.
Monitor on, but blank (power saving mode): 0.23A with the PC Powered on and running: 1.09A
with applications running (e.g. hard disc activity, although I didn’t try with any 3D games etc): 1.13A – 1.17A

PC running with applications, but monitor powered off: 0.85A – 1.01A

PC Suspended: 0.48A
PC Suspended with monitor powered off: 0.45A

There was no noticeable difference whether the printer was powered off, powered on and inactive, or actively printing.

Assuming the PC was left switched on permanently, and using approx 1A as the current, then it will consume about 2100 KWH per year. Assuming about 15p per KWH this is just over £300 per year. Quite an eye opener, although still less than typical cost of a broadband connection.