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ITGlossary · UPS technology
AC Efficiency
Indicates how efficiently a UPS converts incoming AC power into usable output power during normal operation.
Technical level:Intermediate
AC efficiency is expressed as a percentage: whatever energy comes in from the grid and does not reach the output is lost as heat inside the UPS. A UPS with 95% efficiency supplying a 1,900 W load draws about 2,000 W, so roughly 100 W turns into heat.
This figure affects your electricity bill, since a UPS runs around the clock, and it also affects room cooling. Modern online UPS units typically reach 90–96% in normal operation, while ECO mode pushes efficiency higher at the cost of reduced protection.
A common mistake is comparing only the peak figure in the datasheet. Check the efficiency at the load you will actually run, for example 30–50%, where many UPS units perform noticeably worse.
Related terms
- DC EfficiencyMeasures how effectively a UPS converts battery power into output power during battery mode.
- 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.
- Online (Double Conversion) UPSA UPS that continuously converts incoming AC to DC and back to AC, so the load is always fed by the inverter with clean, stable power.
- AutonomyThe time a battery-powered system (like a UPS) can continue operating critical loads after a power failure.
- Cooling FanA built-in fan in UPS or batteries used to dissipate heat during operation.