A white paper released by Mindteck, an IT services and consultancy company, contains data about Windows PC power consumption during idle, low-use and high-use scenarios.

The paper, titled Enabling Green Computing with Windows 7, is primarily  concerned with the benefits of implementing power management policy on Windows 7 computers. However, of probably more interest to our clients, they also investigated the difference between Windows 7 and Windows XP.

Power consumption (Watts)
OS Windows XP Windows 7 Percent improvement
PC Configuration Idle Low High Idle Low High Idle Low High
Older Desktop (P4) 64.2 68.7 106.2 57.3 66.1 79.4 10.75% 3.78% 25.24%
High-end Desktop (Core i7) 50.5 54.3 78.0 45.2 49.1 66.8 10.50% 9.54% 14.36%

 

Windows 7 performs better even with older hardware (Dell Pentium 4 Desktop). These results are for the standard out-of-the-box drivers, but Windows 7 still performs better in every scenario with manually updated drivers for the specific chipset.