I'm always grateful for the input of peers, and struggled with the same issue. Some of the obvious things I had to do (all of which help with the battery drain issue):
- Reduce screen brightness by 50%
- Set light/dark mode to auto (in General settings)
- Check the "low power mode" box in battery management
That didn't fix much. Then came more painful things:
- Switch from Chrome to Safari with all the hassles that come with that such as importing bookmarks, passwords and installing the extensions I like. I'm mostly a PC user so won't be doing that on any other machine ;-). You're probably thinking: wait a minute, the latest Chrome is optimized for Macbook M1. I'm not so sure.
- Considered reinstalling the Mac OS and decided that would make zero difference (as it did for our friend here!)
- Suddenly remembered that battery life had not always been this bad. What was different? A USB hub (with HDMI, USB-C and SD card slots) that I constantly kept plugged in. I unplugged it. Guess what happened.
Battery life back to normal. Peripherals should not do this. But they do, and it's an easy fix.
Sleep mode: yes, the Macbook M1 does lose some power when it sleeps. I didn't measure the drain, but it's noticeable. Maybe it's a coincidence, but I notice that when I turn off wi-fi before I close the lid, the drain is much less to non-existent.
That's an issue you will also run into on quality PC laptops such as the Dell XPS.
And that, folks, concludes my admittedly unscientific findings. (No diagrams or charts). Hope it helps. It solved my problem.
Good night and good luck.