Power saver mode helps to increase battery life.
It reduces the usage of phone features that drain the battery such as the display and data connection.
Home screen, tap
Tap the Power saver
On/Off switch to turn power saver mode on or off.
If you want to choose which phone features to conserve power for, tap
If power saver mode's
option is selected,
HTC One M9(s)
automatically disconnects from the mobile network after 15 minutes when the screen is off and the data connection is idle (no download activity, streaming, or data usage). It reconnects and then disconnects periodically when the data connection is idle to save battery power.
Keep in mind though that the
Sleep mode option for the data connection in
Settings > Power, when enabled, overrides power saver mode.