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ITGlossary · UPS technology
Rightsizing
Selecting UPS capacity to match current load and scale with future needs, avoiding over-sizing.
Technical level:Intermediate
A UPS that is too small for the load gets overloaded and provides very little runtime; one that is far too large costs more, takes up space and runs less efficiently at low load. Rightsizing looks for the right balance between the two.
The process starts from the actual consumption of the equipment in W rather than just the label ratings, adds start-up peaks and the required runtime, and takes growth over the coming years into account. A common target is for the load to use about 60–80% of the UPS rated capacity.
A practical tip: if you expect significant growth, choose a scalable or modular UPS instead of a much larger unit from day one.
Related terms
- Capacity SystemParallel UPS units that share the load with no spare unit (N configuration), so the failure of one unit overloads the rest.
- Offline (Standby) UPSA UPS that leaves the load on the mains and switches to battery only when the mains fails, with a short transfer time; the simplest and cheapest topology.
- 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.
- RedundancyHaving more UPS units or modules than the load needs, typically in an N+1 or 2N configuration, so the load stays powered if one fails.
- Static SwitchA thyristor-based switch with no moving parts that transfers the load between inverter and mains within a fraction of a cycle.
- BypassA path that feeds the load directly from the mains, without protection, when the UPS is overloaded, faulty or under maintenance.