10 October 2026
kVA vs kW, and standby vs prime power, explained
What kVA and kW mean on a generator, how to convert between them, and the difference between standby and prime ratings.
kVA vs kW
kVA (kilovolt-amps) is apparent power — what the generator delivers in total. kW (kilowatts) is real power — what your equipment actually turns into work.
The ratio between them is the power factor. Generators are normally rated at a power factor of 0.8, so kW = kVA × 0.8 and kVA = kW ÷ 0.8. A 200 kVA generator gives about 160 kW.
Standby rating
The standby rating is the most a generator can deliver during a mains power cut, for a limited number of hours per year. It's the right figure for backup generators that sit idle most of the time.
Prime rating
The prime rating is what the generator can supply for unlimited hours at a varying load. It's around 10% lower than standby. Use it when the generator is the main source of power — remote sites, construction, off-grid.
Which should I look at?
Backup for a building: standby. Main power: prime. Every model page on our site shows both figures side by side.