Research: actual power usage modern PC's

Test

To show you the power usage of a PC we built ten configurations, 5 with an AMD prcessor and 5 with an Intel processor. The configurations differ from ultra high-end (with the fastest processor and graphics card available) to a simple budget PC.

We have used the following Intel processors: Celeron D 351, Pentium 4 530, Pentium D 805, Core 2 Duo E6700 and the Core 2 Extreme X6800. From AMD we used a Sempron 3400+, a Athlon 64 3000+, Athlon 64 X2 4200+, Athlon 64 X2 5000+ and the high-end Athlon 64 FX-62. To make the test as real-life as possible we combined budget processors with budget graphics and balanced all systems as well as possible. The cards used from budget to high-end are a GeForce 7300GS, 6600GT, 7600GT, 7900GTX and in the high-end system we used a SLI or CrossFire configuration of two GeForce7900GTX cards and two AI Radeon X1950 cards.

To measure the actual power usage we used a EMU power meter. The usage is measured in seven situations; when the PC is off, hibernates, stand by mode (S1 and S3), idle, high processor usage (PCMark 05 CPU test), and high processor and graphics use (3D Mark 06 3D benchmark).

Measure the usage yourself

It is fairly easy to keep track of the actual power usage of your machines yourself, any respectable DIY shop sells power meters, and they do not cost the earth. The usage is measured in Watts, and the total usage over a period of time usually is stated in KiloWatts per Hour (KWh). Your energy supplier will state the amount of KWh's you have used in a period in your statements as well.

A KWh is the amount of power a device of 1000W would use in an hour, so for example if your PC would use 250 Watt average, it would use 1 KWh in the space of four hours. The costs of a unit will differ per supplier, however you can calculate the average cost of an electrical appliance according to the following formula :

(Average Usage / 1000) x Average usage hours per day x 365 x Price per kWh

A small example : A PC runs 24/7 and uses 150 Watt average, one KWh costs 11 pence, this would come to a total cost of : (150 / 1000) x 24 x 365 x 0,11 = £ 144.54 per year.

Our tests show that the cheaper power meters can be quite inaccurate, especially when measuring low values This makes it very difficult to measure the actual usage in "standby" or "off" mode. Higher values (when an applicance is "on" or running) are measured accurately by all meters, also the cheaper ones. The professional meter we have used in our tests does give accurate values for both low and high values.