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ITGlossary · Electrical units
Watt (W)
The unit of real power; on a UPS it shows how much power connected equipment can actually draw.
Technical level:Basic
The watt measures real (active) power, that is, the energy a device consumes per second and converts into work or heat. One watt equals one joule per second, and the energy consumption on your bill is measured in kilowatt-hours (kWh).
UPS power is given in two quantities: VA (apparent power) and W (active power). They are linked by the power factor: a 1000 VA UPS with a factor of 0.6 delivers 600 W, while with a factor of 0.9 it delivers 900 W. Your load must stay within both limits.
A common mistake is comparing equipment consumption only with the UPS VA rating. Add up the actual W of the equipment (from the label or by measurement) and compare it with the rated power in W.
Related articles
Related terms
- kVA (kilovolt-ampere)A unit of apparent power equal to 1,000 VA, used to rate UPS systems; real power in kW equals kVA × power factor.
- Peak LoadThe highest amount of power drawn by connected equipment during operation.
- Hardwired (Terminal Block) ConnectionPermanent connection of the UPS input or output by an electrician, with cables screwed into a terminal block instead of plugs and sockets, usually on higher-power UPS units.
- IEC C13/C14 ConnectorsStandardised pair of connectors rated up to 10 A under IEC 60320, found on UPS outputs and on the power supplies of computers, servers and monitors.
- IEC C19/C20 ConnectorsPair of connectors rated up to 16 A under IEC 60320, used on higher-power UPS units, rack PDUs and servers or switches with high-consumption power supplies.
- Input Power CordThe cable that connects the UPS to the wall socket or distribution board, i.e. to its AC power source.