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Power calculation for UPS

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by shangiti

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When I wanted to purchase a UPS for our computer room, vendors asked me what is your KVA requirement. I want to know the formula for calculating this unit and how do we compare it to watts?
Thanks.

3 replies

by xxx123

www.apc.com. They have various kinds of calculators. Of course, they all end up recommending apc products, but you would find out more about your power requirements in the process.

by epepke

Power is calculated by multiplying voltage and current. In the SI, voltage is in volts, current is in amperes (a.k.a. amps), and power is in watts. 1 watt is the same as 1 VA. 1 KVA is the same as 1 kilowatt.

So, why do they say KVA instead of kilowatt? The reason is very silly. They used to say kilowatt all the time. About fifteen years ago, someone decided that there needed to be a special term that meant capacity for power rather than actual power consumed (or produced). The solution was the volt-amp, or VA. Which is the same as a watt, except totally different. This neologism caught on for approximately the same reason that wearing baseball caps backward caught on.

by epepke

Of course, the actual number you give will be bigger than the number of watts you expect to use. You want to provide room not only for future expansion, but a reasonable margin for safety. That, though, is a matter of prudence versus cost, and there's no hard formula.

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