KVA vs. kW: The Crucial Difference That Could Save Your Power Setup
kVA (kilovolt-ampere) measures total apparent power, including the part that does no work. kW (kilowatt) measures actual working power delivered to run your devices. Think of kVA as the whole pizza and kW as the slices you can actually eat.
On a job site, you see a 5 kVA generator labeled “4 kW” and assume it’s under-rated. Contractors often overload rigs because they treat kVA and kW as interchangeable, risking blown fuses and angry clients.
Key Differences
kVA includes reactive power your motors create; kW only counts real power doing the work. Utilities bill kW, but generator specs list kVA to cover peak surges. Always derate kVA by the power factor (typically 0.8) to get usable kW.
Which One Should You Choose?
Match load to kW, then pick a generator rated 20–25% higher in kVA. For a 3 kW server rack, a 5 kVA unit offers safe headroom for startup spikes and future expansion.
Why does my UPS list both kVA and kW?
The kVA shows total capacity; kW shows usable power after accounting for power factor losses.
Can I run a 5 kW load on a 5 kVA generator?
No. At 0.8 power factor, 5 kVA delivers only 4 kW—risking overload and shutdown.