I'm still not sure what is going on. Two Pixel 6a devices running up to date GrapheneOS are experiencing huge battery drains throughout the day. They are setup almost exactly the same with all the same settings and apps.
Both devices need to be recharged 3 times (to 80℅) just to make it through the day. We're not doing any gaming or video streaming.
The owner profile is the only one set to run at all times. There is a private space that closes after screen lock and a few user profiles that are set to not run in the background. We don't even open the private space or other user profiles most days. But I've noticed that even just switching profiles causes a 1-2℅ battery hit.
Play Services are installed on all profiles. Most other apps are set to restrict battery when not in use and to turn off background data. The phones are mostly on WiFi.
Location Services are set to use Google WiFi location services, but location is globally turned off 99℅ of the time in an attempt to save battery life.
I only run 1-3 apps simultaneously and close apps that are not in use frequently. Everything is set to dark mode and night light + extra dim is used in the evening.
Background processes take up most of the battery drain according to battery usage, with 45℅ coming from System Idle, 30℅ from WhatsApp background, and 12℅ from Play Services background.
I switched these phones to GrapheneOS about 1.5 months ago. On stock, they had very good battery life lasting 1-3 days depending on usage. Battery was slightly worse after switching, but it got really bad in the last week or two.