Understanding Generator Power Ratings Prime, Standby and Continuous Power

Dec 14,2021

When purchasing a generator for your home or business, there are a few considerations you need to keep in mind. One of the most important aspects to think about is how the generator will be used.

With a lot of information available, it’s easy to get confused with all the technical jargon, facts and figures found online. So, let’s begin with the power ratings of diesel generators.

International Standard for Diesel Generators

Under ISO 8528 Reciprocating internal combustion engine driven alternating current generating sets, there are four key power ratings that diesel gensets can be categorised under:

  • Prime Power (PRP)
  • Emergency Standby Power (ESP)
  • Limited-Time Running Power (LTP)
  • Continuous Power (COP)

The components that make up the power rating of a generator are annual run time, load variability and average load factor. It’s important to remember that a genset can be used according to different ratings, however, the performance of the genset will vary.

Prime Power Generators

A prime generator is often used as a main source of power when there is no utility source available. They can support variable loads over a period of time and are primarily used for industrial applications like mining and construction sites and in remote areas where access to the grid is not available.

Under ISO 8528, the expected annual run time of a prime genset is unlimited with an average load factor of 70% + of the prime rating. Prime generators need to be reliable and durable. PowerLink’s classic range of diesel generators are suitable for all prime applications. With a power output of 7kVA to 3,250kVA, PowerLink’s diesel gensets are powered by reputable engine brands, like CumminsKubotaPerkins and Baudouin, and are available in open set, canopy and containerised options.

Emergency Standby Generators

As the name suggests, standby generators are used in emergency situations or when there is a power outage. They are used across numerous industries that need reliable power like healthcare, construction, data as well as by homes and businesses in rural and remote locations.

Unlike a prime power generator, a standby generator is designed to have a limited usage per year (approx. less than 200 hours per year with an average load factor of 70% + of the standby rating) but can support variable loads, like a prime genset.

For a complete, automated emergency power solution, a backup diesel generator can be wired to an Automatic Transfer Switch (ATS) which is then in turn connected to the main power grid. When the ATS detects a fluctuation in the main current, it will automatically switch the circuit and start the generator.

An ideal standby generator will be designed with a reliable engine, a long-life span and a large fuel tank so that it can be used for extended periods without needing to be constantly refuelled. The PowerLink QSV range, with a power output from 10kVA to 2,500kVA, are compact and durable, making them an excellent backup genset option for residential and commercial applications.

Limited Time Running Power Generators

Generators that have a Limited-Time Running Power rating are able to operate with an undefined load variability for up to an expected annual run time of 500 hours or less. They also have an average load factor of 100% + of the prime rating.

Continuous Power Generators

Continuous power generators are very similar to prime power generators. They have an unlimited expected annual run time like a prime generator; however, they require a constant load variability, have a 100% average load factor and cannot be overloaded unlike a prime generator.

Continuous generators are mostly used in remote locations and are an ideal solution for base load applications i.e. operating pumps on farms, ventilation systems in underground mines and land refuge remediation sites.

Continuous power generators are not limited to diesel generators. Gas generators and biogas cogeneration systems can also be suitable forms of continuous power. PowerLink has a complete range of natural gas generators, soundproof cogeneration and biogas cogeneration units that can deliver between 10kW and 2000KW of power.

Whether you have a prime, standby or continuous application, PowerLink has a power generation solution to meet your needs. We understand the Australian landscape and are here to discuss the best option for you. For more information, email us at and we will direct you to your nearest PowerLink distributor.

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