Calculate alternator output power, current and derating for temperature and power factor.
Generators are rated in kVA at a reference temperature and altitude. Both hot ambient conditions and thin air at altitude reduce cooling capacity, so the usable rating falls before power factor is even considered. A 100 kVA set in a hot plant room may deliver only 76 kW, which is why generator sizing so often disappoints on commissioning.
Alternator Output
Available kW = nameplate kVA × (1 − derating) × power factor
Available kW = nameplate kVA × (1 − derating) × power factor Generators are rated in kVA at a reference temperature and altitude. Both hot ambient conditions and thin air at altitude reduce cooling capacity, so the usable rating falls before power factor is even considered.
A 100 kVA set in a hot plant room may deliver only 76 kW, which is why generator sizing so often disappoints on commissioning.
This calculator takes 5 inputs: Nameplate rating, Load power factor, Line voltage, Derating for ambient temperature, Derating for altitude. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.