How to measure power consumption
To monitor the laptop's power consumption while it is running, unplug the AC power and run:
# watch -n1 'cat /proc/acpi/battery/BAT0/*'
This requires ACPI to be enabled. Note that running on battery power may activate power-saving mechanisms, so unless you take care to deactivate them this does not reflect power consumption under AC power.
To measure power consumption while the laptop is suspended, use the ACPI sleep power drain test script.
For reducing power consumption, see How to reduce power consumption.