UltraPowerSaver uses unique methods to reduce CPU power requirements to allow your device's battery to last for days at a time. These features include a resolution downscale, an aggressive doze mode on sleep, as well as a ton of other features.

Featues:
- Downscales resolution
- Reduces CPU power requirements
- Aggressive sleep algorithm
- Activates system-wide low-power mode
- Decreases brightness

Without UltraPowerSaver:
- Battery estimates (mathematically) 1 DAY from 100% to 0% with full usage.

With UltraPowerSaver:
- Battery estimates (mathematically) 4 DAYS from 100% to 0% with full usage.

WARNING:
There is a KNOWN ISSUE with rebooting with UltraPowerSaver mode enabled. You will need to disable it before rebooting to prevent this glitch.

A workaround is to rotate your screen. This can be from the lock screen (if your device supports it) or from any other app (Settings is easiest to enter).

Although these results were gathered from my device, I cannot guarantee you will experience the same results.