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ITFrequently Asked Questions · UPS
Which type of UPS should I choose?
Line Interactive UPS: affordable, with a short transfer time (ms) and a simulated sine wave output. Online UPS: zero transfer time, pure sine wave output, and strong voltage regulation for sensitive loads.
The choice depends mainly on how sensitive the load is and on the quality of the mains supply in your area. A line-interactive UPS corrects small sags and swells with a built-in AVR and switches to battery only when the voltage goes out of range. For an office PC, router, NAS or alarm system it is usually enough.
An OnLine (double-conversion) UPS continuously converts AC to DC and back to AC, so the load is always fed by the inverter and never "sees" a transfer. It is the preferred choice for servers, medical and laboratory equipment, industrial controllers and boilers with electronics, as well as in areas with frequent fluctuations or where power comes from a generator.
As a rule of thumb: the more critical the load and the less stable the grid, the more an OnLine unit is justified, at the cost of a higher price, slightly higher losses and a fan that runs all the time.
A common mistake is choosing a UPS by VA alone. First check the real power in W of your devices, allow a margin of about 20–30%, and make sure that devices with PFC power supplies work well with the output waveform.
