What is a kVA, and how do you calculate it?
A kVA is one thousand volt-amperes — a measure of apparent power, meaning everything the electrical system draws, not only the part that does useful work. kW measures that useful portion. The two are linked by the power factor: kW = kVA x PF. Colo Solutions quotes colocation power in kW because that is what a customer's equipment actually consumes, while UPS and generator plant is rated in kVA.
| kVA | Apparent power, in thousands of volt-amperes |
|---|---|
| kW | Real power — the portion converted to useful work |
| Relationship | kW = kVA x power factor (PF) |
| Typical UPS PF | 0.8 to 1.0 depending on equipment and load |
| How Colo Solutions bills | Colocation power is sold in kW |
The short version
kVA is apparent power. kW is real power. The power factor is the ratio between them.
An electrical system draws a certain amount of current at a certain voltage. Multiply them and you get volt-amperes — apparent power. But not all of that becomes useful work: some is reactive, sustaining magnetic fields in motors and power supplies rather than doing anything you would notice. The portion that does useful work is real power, measured in kilowatts.
Calculating it
The relationship is one formula:
kW = kVA x PF
A power factor of 1 means the system is perfectly efficient — every volt-ampere becomes a watt. Real equipment sits below that.
Worked example: a 600 kVA UPS with a power factor of 0.8 delivers 480 kW of real power. Buy that UPS expecting 600 kW of usable capacity and you are 20% short before a single server is racked.
Rearranged, to size plant from a known load: kVA = kW / PF.
Why the distinction matters when buying colocation
It is the difference between what you are billed for and what your equipment can actually draw.
Colocation power is normally sold in kW, because that is what your equipment consumes. Facility plant — UPS systems, generators — is normally rated in kVA, because that is what the equipment must be built to carry. Comparing a quote in one unit against a specification in the other, without applying the power factor, will mislead you in the direction of thinking you have more headroom than you do.
Two practical consequences:
- When comparing providers, confirm the unit. A cabinet advertised at “5 kVA” is not the same as one at 5 kW. At a 0.8 power factor it is 4 kW.
- When sizing your own deployment, measure real draw rather than adding up nameplate ratings. Nameplate is a maximum, and summing maximums produces a number well above what the equipment ever pulls — which leads to buying capacity you never use.
What Colo Solutions does
We quote colocation in kW, and we would rather talk about your measured draw than your nameplate total. If you are unsure what your equipment actually consumes, that is a normal thing not to know, and it is worth establishing before you size a cabinet — over-provisioning is the most common and most expensive mistake in a colocation contract.