PowerTOP is a Linux tool to diagnose issues with power consumption and power management. In addition to being a diagnostic tool, PowerTOP also has an interactive mode where you can experiment with various power management settings for cases where the Linux distribution has not enabled those settings.
PowerTOP reports which components in the system are most likely to blame for a higher-than-needed power consumption, ranging from software applications to active components in the system. Detailed screens are available for CPU C and P states, device activity, and software activity.