Adjustable voltage sensitivity allows the UPS to optimize performance according to the specific power supply environment or generator application. Warning tones notify users when the status of the power supply or UPS system changes. An automatic self-test conducts periodic battery self-tests to timely replace depleted batteries. The battery charge indicator shows when the battery is charging and when the charging process is complete. Battery failure notifications enable analyses for early detection of battery faults for timely preventive maintenance. Battery-supported outputs and outputs with surge protection reserve capacity and backup time for connected devices that need to switch to UPS battery operation in an emergency; less critical devices are only protected against surges. A wiring problem indicator signals potentially hazardous wiring issues in the in-wall cabling.