Generator Sizing Made Simple: What kVA Really Means

Generator brochures speak kVA; your equipment nameplates speak kW and amps. Getting a genset that actually holds your load starts with three facts.

Fact one and two: kVA vs kW, and starting surge

First, kVA times power factor equals kW — and for mixed industrial loads the factor is about 0.8, so a 100 kVA set delivers roughly 80 kW of real work. Second, electric motors gulp several times their running current for the seconds they start: a 15 kW compressor motor can demand the output of a 50 kVA set just to spin up. Size for the biggest motor starting while everything else runs, not for the sum of nameplates alone.

Fact three: diesels hate loafing

A diesel genset wants to work at 60 to 80 percent load. Run it week after week at 20 percent and unburned fuel glazes the cylinders — the "wet stacking" that shortens engine life and shows up as oily exhaust. So resist the urge to double everything "to be safe"; the oversized set costs more to buy, more to feed, and dies younger.

On a used set, check the hour meter against the service book, inspect for wet-stacking residue at the exhaust, and always witness a load test — a genset that only ever ran idle in a showroom has its own kind of wear.