A DC-UPS is an uninterruptible power system that takes in primary power (usually utility AC) and outputs DC voltage while providing backup power from the integrated batteries in the event the incoming (utility AC) power is lost.The most common DC (direct current) voltages in use are 48, 24, and 12 volts, but other or multiple voltages are available.

AC-UPSs input AC Power and output AC Power. If your end-point devices require DC input, you must convert the UPS AC output power to DC with a rectifier or a separate AC to DC power supply. This adds costs and requires a larger UPS to account for the power loss in converting to DC. DC power systems are less costly to operate than AC systems. They consume less power since only one internal power conversion (from AC to DC) is needed, as opposed to two internal conversions (AC to DC back to AC) in AC-UPSs. Fewer power conversions reduce the BTUs the system dissipates, thereby reducing cooling requirements. These factors can reduce electrical consumption by up to 25% over AC-UPSs.