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ge:prime-vs-standby

Prime Power vs Standby Power Ratings

Most generator sets are sold for “backup” power, to supply electricity when the utility power has failed. These are rated as “standby” generators, and while rated as “Continuous” duty – meaning they will not overheat if used continuously – this is an “emergency” rating, not a rating for long life of the generator end or engine.

“Prime Power” is the rating that should be used when a generator is to supply power in place of utility power, or in cases where it will supply power for significant portions of time on a regular basis when utility power is less than reliable.

We recommend purchasing generator sets based on the Prime Power ratings, even when they will be used for standby power in developing countries. This will result in longer life and better return on the investment.

:: PRP :: Prime Power

The prime power gen-set engine rating is the nominal power an engine is capable of delivering with a variable load for an unlimited number of hours per year with normal maintenance intervals observed. This rating incorporates a 10% overload capability which is available for up to 2 hours at a time. Operating time between 100 % and 110% of the prime power rating is not to exceed 8% of the total engine operating time. This rating conforms to ISO 8528-1 “prime power (PRP)”. The permissible average power for the prime or PRP rating is not to exceed 70% of rated prime power when calculated per ISO 8528-1.

:: ESP :: Standby Power

The standby gen-set engine rating is the nominal engine power available at varying load factors for up to 200 hours per year with normal maintenance intervals observed. No overload capability is available for this rating. This rating conforms to ISO 8528-1 “Emergency Standby Power (ESP)”. The permissible average power for the standby or ESP rating is calculated per ISO 8528-1.

:: COP :: Continuous Power or Baseload Power

Applicable for supplying power continuously to a constant 100% load for unlimited hours. Continuous Power (COP) in accordance with ISO 8528, ISO 3046, AS 2789, DIN6271 and BS 5514.


Power Rating Application Guidelines: Summary

Power Rating Normal Operating Mode Limitations Peak Operating Mode Limitations Typical Application
Maximum Average Load Maximum Operating
Time per Year
Maximum Power Maximum Operating
Time per Year
Standby Power 80% of Standby Power 200 hours Standby Power 25 hours Emergency Standby
Prime Power
- Unlimited Time -
70% of Prime Power
(during any 250 hour
operating period)
Unlimited (1) Prime Power + 10% 25 hours Unreliable Utility Power
Marine Auxiliary
Head-end equipment
Rental equipment
(2) Prime Power 500 hours
Prime Power
- Limited Time -
100% of Prime Power 750 hours Prime Power 750 hours Peak Shaving
Utility Power Curtailment
Continuous Power 100% of Continuous Power Unlimited Continuous Power Unlimited Utility Power
Electric Marine Propulsion
Cogeneration
ge/prime-vs-standby.txt · Last modified: 2024/06/27 19:27 by Alan Shea