Various embodiments of the present technology provide methods for determining a status of power supplies to a server system and dynamically managing an uninterruptible power system (UPS) of the server system between an off-line mode and an on-line mode based upon the status of the power supplies. The UPS requires a minimum standby power during the off-line mode while requires no switch time to continuously supply power to loads of the server system during the on-line mode. Some embodiments determine a status of an AC input power to a server system and, in response to detecting an abnormal condition associated with the AC input power, generate a power warning signal. The power warning signal can cause an UPS of the server system to be switched from an off-line mode to an on-line mode.