The International Standards Organization (ISO) 8528-1 defines three types of duty:
***Continuous Operating Power (COP)
***Prime Running Power (PRP)
***Limited-Time running Power (LTP)

Limited-Time Running Power (LTP) (หรือพิกัดแบบสำรองฉุกเฉิน Standby Rating)
Limited-time running power is the maximum power that a generator set delivers for up to
500 hours per year under stated ambient conditions. Only 300 hours can be continuous running. Maintenance according to the manufacturer must be followed to reach these standards.

Prime Running Power (PRP) (หรือพิกัดแบบต้นกำลัง)
Prime running power is the maximum power a generator set has during a variable power sequence for an unlimited number of hours under stated ambient conditions. Maintenance
according to the manufacturer must be followed to reach these standards.

Continuous Operating Power (COP) (หรือพิกัดแบบต่อเนื่อง)
Continuous operating power is the power a generator set can operate at a continuous
load for an unlimited number of hours under stated ambient conditions. Maintenance
according to the manufacturer must be followed to reach these standards.