Power-profiles-daemons is a free and open source project designed to handle system power profiles over D-Bus. The two major Linux desktop environment, GNOME and KDE Plasma, are nicely integrated with it, allowing the user to easily manage power profiles from their dedicated power manager interfaces, but it is also possible to switch profiles and retrieve information about them from the command line, using a dedicated utility.
powersave
How to optimize laptop battery life with TLP on Linux
When using Linux on mobile devices such as Laptops, it is very important to tune the right kernel parameters in order to optimize battery life. Tlp is a highly customizable, free and open source command line utility released under the GPLv2 license (the source code is hosted on github) created with this exact goal.