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ITGlossary · UPS technology
DC Efficiency
Measures how effectively a UPS converts battery power into output power during battery mode.
Technical level:Intermediate
When a UPS runs on battery, the inverter converts the battery's direct voltage into alternating voltage. Part of the energy is lost as heat in this conversion. DC efficiency shows how much of the battery's energy actually reaches your loads.
This figure directly affects runtime. With the same battery and the same load, a UPS with higher DC efficiency will last longer. In general, systems with a higher battery voltage work with lower currents and have fewer losses in cables and electronics.
A common mistake is calculating runtime only from the battery's watt-hours and the load's power, as if there were no losses. Use the manufacturer's runtime tables, or take DC efficiency into account in your calculation.
Related terms
- AC EfficiencyIndicates how efficiently a UPS converts incoming AC power into usable output power during normal operation.
- Charging Modes (Mode 1–4)The IEC 61851 classification of EV charging, from a plain socket with no communication (Mode 1) to a DC fast charger (Mode 4).
- Double Conversion EfficiencyThe share of input power that an online UPS delivers to its output, lower at light load and highest at medium to high load.
- InverterThe component inside a UPS that converts DC power from batteries back to usable AC power.
- AutonomyThe time a battery-powered system (like a UPS) can continue operating critical loads after a power failure.
- Cold Start FunctionA feature that allows a UPS to be started directly from the battery without utility power.