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ITGlossary · UPS technology
Double Conversion Efficiency
The share of input power that an online UPS delivers to its output, lower at light load and highest at medium to high load.
Technical level:Advanced
The efficiency of an online UPS is not constant; it varies with the load percentage. At very low load, the fixed losses of the electronics make up a large share of total consumption and efficiency drops noticeably. As the load rises, efficiency increases, and in modern systems it typically reaches about 94–96% at medium and high loads.
This curve matters in practice when sizing. A UPS that is far too large for its load will run permanently in the low-efficiency range, with higher consumption and more heat.
Practical tip: choose the rating so that the normal load sits at roughly 40–80% of nominal capacity, leaving room for expansion. Ask the manufacturer for the efficiency curve, not just the peak value.
Related terms
- 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.
- AC EfficiencyIndicates how efficiently a UPS converts incoming AC power into usable output power during normal operation.
- DC EfficiencyMeasures how effectively a UPS converts battery power into output power during battery mode.
- Capacity SystemParallel UPS units that share the load with no spare unit (N configuration), so the failure of one unit overloads the rest.
- InverterThe component inside a UPS that converts DC power from batteries back to usable AC power.
- Zero Transfer TimeA feature of online UPS systems, where the inverter feeds the load continuously so a power cut causes no gap at all.