TUI

sudo powertop

It needs to run for a little while to collect data. It's also a good idea to calibrate it once in a while.

Calibrate

sudo powertop --calibrate

This will turn off your display and later wifi. It takes a little while to run through everything and it's best to not use the computer while this is going on for the most accurate results.

HTML

sudo powertop --html=powerreport.html

Generates a nice readable html report. Usually this is easier to understand than the TUI results.