"PowerTOP is a Linux tool that finds the software component(s)
that make your laptop use more power than necessary while it is
idle. As of Linux kernel version 2.6.21, the kernel no longer has a
fixed 1000Hz timer tick. This will (in theory) give a huge power
savings because the CPU stays in low power mode for longer periods
of time during system idle.
"However... there are many things that can ruin the party, both
inside the kernel and in userspace. PowerTOP combines various
sources of information from the kernel into one convenient screen
so that you can see how well your system is doing, and which
components are the biggest problem..."