What does 1000VA mean?

VA stands for volt-amperes. A 1000VA rating is a measure of apparent power: volts multiplied by amps. On a UPS, it tells you how much power the unit can supply, but the usable amount in watts is lower.

VA vs watts

Watts are the real power your equipment uses. VA is the apparent power. They are linked by the power factor:

Watts = VA × power factor

• A 1000VA UPS with a power factor of 0.6 supplies 600 W.
• A 1000VA UPS with a power factor of 0.9 supplies 900 W.
• A 1000VA UPS with a power factor of 1.0 supplies 1,000 W.

Always check the watt rating printed on the UPS label or spec sheet. It is the number that counts when you add up your load.

What can a 1000VA UPS run?

A typical 1000VA unit rated around 600 W can run:

• One desktop PC and a monitor, plus a router and modem.
• A small home office setup.
• A network switch and a small NAS.

It is not made for space heaters, laser printers, large gaming rigs with high-end GPUs or air conditioners.

How to size one

1. Add the watts of the devices you want to protect.
2. Add 20 to 25 percent headroom.
3. Choose a UPS whose watt rating is above that total.
4. Check the runtime chart to see how many minutes you will get.

Example

A PC at 250 W, a monitor at 40 W and a router at 15 W total 305 W. With 25 percent headroom you need about 380 W. A 1000VA UPS rated at 600 W covers this with room to spare.

Runtime shrinks as the load rises, so a smaller load gives longer battery time.