Computer programs can make your computer use more power. PowerTOP is a Linux tool that helps you find those programs that are misbehaving while your computer is idle. The application that misbehaved the most was the Linux kernel. However, as of version 2.6.21, the Linux kernel went tickless, and no longer has a fixed 1000Hz timer tick. The result (in theory) is huge power savings because the CPU stays in low power mode for longer periods during system idle.