Optimize energy settings for a portable Mac
If you have a portable Mac, you can optimize your computer’s energy use to get the longest battery life when it’s not plugged into a power outlet or to get the best performance when it’s plugged in.
On your Mac, choose Apple menu > System Preferences, then click Energy Saver.
You can set the computer or display to sleep at different times when you’re using the battery or connected to power.
Set sleep times for battery use: Click Battery, then drag the “Computer sleep” and “Display sleep” sliders, or the “Turn display off after” slider.
Set sleep times for power adapter use: Click Power Adapter, then drag the “Computer sleep” and “Display sleep” sliders, or the “Turn display off after” slider.
To save energy, select “Put hard disks to sleep when possible” in the Battery or Power Adapter pane.
To keep your display dimmed while using your battery, select “Slightly dim the display while on battery power” in the Battery pane.