Yesterday I compared power consumption between two different versions of Ubuntu. I dual boot installed Ubuntu Intrepid and Jaunty on a Dell Inspiron 6400 laptop (Dual core 1.6GHz, 1MB RAM) and installed powertop and also DVD reading software using packages from Medibuntu. I then removed the battery from the laptop and plugged the mains power adapter into a power meter to measure power consumption.
My aim was to benchmark the power consumption for three scenarios:
1) Idle for 10 minutes
2) Running Firefox on 3 Flash enabled sites (slashdot.com, news.bbc.co.uk and digg.com) for 10 minutes
3) Playing 4 minutes from a DVD
I ran powertop to look at how much time the system was in the C0 state (CPU running) and to observe the number of Wakeups-from-idle per second. I also installed sensors-applet to monitor CPU and HDD temperature changes during the benchmarking.
In the Idle case, Intrepid was waking up ~60.5 times a second and drawing 30.0 Watts while Jaunty was waking up ~56.8 times a second and drawing 29.2 Watts, so there was some power saving improvement with Jaunty. CPU temperatures were comparable at 42 degrees C (which is quite hot!). There was very little difference between times in C0 (running) states between Intrepid and Jaunty.
For the Firefox test the number of wakeups was difficult to get a stable measurement, since the flash was generating a lot of irregular activity and so it was difficult to compare like for like. Intrepid was drawing ~30.6 Watts and the CPU was ~43.5 degrees C, where as for Jaunty I observed ~29.3 Watts and a higher temperature of ~45.4 degrees C, which is a little perplexing.
Finally, for the VLC DVD playing test. Intrepid drew 35.7 Watts and the CPU warmed to 49.3 degrees C while Jaunty drew 35.0 Watts and warmed to 51.8 degrees C (again a little perplexing why it's warmer and drew less power overall).
From my crude set of tests we can see that Jaunty does seem to show some power improvements in all three test scenarios. As yet, I'm perplexed why Jaunty is drawing less power but the CPU is getting slightly warmer in the non-idle tests; this needs further investigation (any ideas why?)