The macOS 12 Monterey and iPadOS 15 updates that Apple introduced today bring a key iPhone feature over to the Mac and iPad -- Low Power Mode. On Apple's Monterey page that breaks down all of the new updates, there's a listing for Low Power Mode.
According to Apple, Low Power Mode on Mac reduces the system clock speed and the display brightness in order to extend your battery life even further. This means that if you're doing less intensive tasks like watching videos or browsing the web, you can eke even more out of your Mac's battery.
On the Mac, Low Power Mode is compatible with the MacBook (Early 2016 and later) and MacBook Pro (Early 2016 and later).
There is no mention of Low Power Mode on Apple's iPadOS 15 page, but there is a Low Power Mode feature available after installing the update.
Top Rated Comments
At least that’s what it says on the webpage.
EDIT: Apparently, the MacBook Air supports it (at least the M1 MBA) just like @.player pointed out. Don’t be sad.