Power explanations according to ISO 8528 standard:
Ambient conditions according to standard ISO 8528-1: 2005: 1000 mbar, 25ºC, 30% relative humidity
Prime Power (PRP)
Maximum power which a generating set is capable of delivering continuously whilst supplying a variable electrical load when operated for an unlimited number of hours per year according to ISO 8528. 10% overload capability is available for a period.
Emergency Standby Power (ESP)
Maximum power at variable load under the operating conditions for which a generator set is capable of delivering, up to 200 operating hours per year, according to ISO 8528. Overload is not allowed.