powerconsuption low at the beginning

[Baeckham]

Hi,

I am running a intel core2duo laptop with 64 bit gentoo linux (amd64) on. I am 
observing the power consumption with an external device which is switched 
between power outlet and my laptop.

Today I recognized a strange behavior. After I started up the system I got a 
very low power consumption - between 5 and 9 W. After a while (about 5 -10 
minutes) and I did not do anything special the power consumption raised to 25 
W and never get under 25W again. All the time the system is idle. No extra 
programs where started, no special happed. I can not see any special log 
entry in my syslog ...

Any ideas what could cause this or how to find out?
Powertop shows this when the system is idle and uses about 25W:
Wakeups-from-idle per second : 287.0    interval: 10.0s
no ACPI power usage estimate available

Top causes for wakeups:
  23.4% ( 60.2)       <interrupt> : extra timer interrupt
  13.8% ( 35.6)           gkrellm : schedule_timeout (process_timeout)
  13.0% ( 33.4)              java : futex_wait (hrtimer_wakeup)
   9.0% ( 23.2)       <interrupt> : eth0
   6.5% ( 16.8)      <kernel IPI> : Rescheduling interrupts
   5.4% ( 13.8)             artsd : schedule_timeout (process_timeout)
   4.9% ( 12.7)            kicker : schedule_timeout (process_timeout)
   4.8% ( 12.5)        kclock.kss : schedule_timeout (process_timeout)
   4.4% ( 11.4)                 X : do_setitimer (it_real_fn)
   2.4% (  6.3)       soffice.bin : schedule_timeout (process_timeout)
   1.7% (  4.4)       firefox-bin : futex_wait (hrtimer_wakeup)
   1.6% (  4.0)   <kernel module> : usb_hcd_poll_rh_status (rh_timer_func)
   1.4% (  3.7)       <interrupt> : acpi
   1.0% (  2.5)              java : schedule_timeout (process_timeout)
   0.9% (  2.2)           klipper : schedule_timeout (process_timeout)
   0.8% (  2.0)        kpowersave : schedule_timeout (process_timeout)

Steffen