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.
For PowerTOP to work best, use a Linux kernel with the tickless idle and highres timer stats (NO_HZ, CONFIG_HIGH_RES_TIMERS, CONFIG_TIMER_STATS) feature enabled (version 2.6.21 or later). Currently, only 32-bit kernels have support for tickless idle; 64-bit kernels are expected to gain this feature in version 2.6.24.
PowerTOP works best on a laptop computer, or at least a computer with an Intel mobile processor (certain small non-laptop devices also contain a mobile processor). When using PowerTOP on a laptop, do so when running on battery.