Quick, what is the biggest drain on your laptop's battery?
If you answered "the display," you're right -- for the most part.
The single biggest occupier of battery resources, day in and day out, is your laptop's display. More specifically, it's the that energy goes into powering the backlight that illuminates the pixels on your laptop's display.
The obvious move to extend battery life is then to lower your display's brightness. On either a Windows 10 laptop or an Apple MacBook, you can usually do this on the keyboard, but there are a couple other settings to change that will help automate the process.