It's also interesting that this low-power mode is sufficiently low power for Apple to be feel comfortable sipping battery power continually. Any guesses about how much power this mode actually uses?
An iPhone has at least 10 000 mWh battery capacity (depends on model), so in 1 month something like this consumes around 0.6 percentage points of battery.
https://support.apple.com/en-us/HT209495#:~:text=power%20res....
what?
But if you used up the battery and not charge for a long time (1 months or so). This can happen because batteries discharge themselves slightly even not being used.