I am running Ubuntu 10.10 on my Dell Studio XPS 1640 and have about one hour of battery life in it, compared to about 2.5 hours running on Windows 7.

This is with wireless and bluetooth on, but still, the difference seems incredible.

What could be causing such a difference and is there a way to close the gap without losing core functionality?

EDIT: here's some output from powertop. This is with bluetooth turned off and Wifi turned on. The output seems pretty normal to me, but as indicated, this is about 1 hour of battery life on a full battery...

Wakeups-from-idle per second : 476.2    interval: 10.0s
Power usage (ACPI estimate): 2.5W (1.2 hours)

Top causes for wakeups:
  30.0% (167.2)D  chrome
  21.0% (117.3)   [extra timer interrupt]
  13.9% ( 77.4)   [kernel scheduler] Load balancing tick
   3.4% ( 18.9)D  xchat
   7.1% ( 39.8)   [iwlagn] <interrupt>
   5.9% ( 32.9)   AptanaStudio3
   3.9% ( 21.6)D  java
   2.7% ( 14.9)   [TLB shootdowns] <kernel IPI>
   2.5% ( 14.1)   docky
   1.8% ( 10.0)   nautilus
   1.6% (  9.0)   thunderbird-bin
   1.0% (  5.5)   [ahci] <interrupt>
   0.9% (  5.0)   syndaemon
   0.8% (  4.3)   [kernel core] hrtimer_start (tick_sched_timer)

EDIT: after changing /proc/sys/vm/laptop_mode to 5 (it was set to 0), wakeups seem to have decreased, although usage still seems far too high:

Wakeups-from-idle per second : 263.8    interval: 10.0s
Power usage (ACPI estimate): 2.6W (0.9 hours)

EDIT: I seem to have discovered the main cause: I was using the open source ATI Drivers. I recently installed the official ATI drivers and laptop battery life seems to have doubled since.

EDIT: last edit. The previous 'solution' of installing the official ATI drivers turns out to be a non-solution. Although it does increase battery life, my laptop resolution is maxed out at 1200x800 after a reboot. (Please note that this problem does not need answering in this question as it is a seperate case)