For the first test, we had measured the power consumption using the SeaSonic PowerAngel as it was attached to the ThinkPad's AC power adapter. The oldest Ubuntu release we had tested (Ubuntu 5.04) had consumed the most power while idling but to some surprise, Ubuntu 7.10 was not the most power efficient. In our idle tests, Ubuntu 7.10 loaded up on the R52 notebook had consumed 29 Watts while Ubuntu 6.06.1 had led the pact with 27 Watts and both Ubuntu 5.10 and 6.10 were at 28 Watts. However, Gutsy's 29 Watts was four less than the power-hungry Hoary Hedgehog. While Ubuntu 7.10 has the tickless kernel feature and other power optimizations, there is more software running on the newer releases (such as Network Manager) that likely explains these power results.
While the system was under load, Ubuntu 7.10 was actually tied for second with Ubuntu 6.10 for the most power consumption. Consuming the most power was Ubuntu 7.04 with 51 Watts under load while Ubuntu 7.10 and 6.10 were at 50 Watts.