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Article Date: 30th June 2020

Advanced - Prime Power vs Standby Power

Advanced, prime power vs Standby Power

The Difference Between Prime & Standby - Generator Power Ratings Explained

If you’ve spent time searching for a generator for your home, business or recreation, you will more than likely have stumbled across the phrases “prime rated” and “standby rated”.

But what exactly does this mean?

Simply put, these terms refer to how much power the generator can supply in 2 different use cases:

Standby Power - When a generator is used as a backup to mains supply power.

Prime Power - When a generator is used as a primary power source.

With these basic definitions in mind, let’s dive deeper into each power rating and what scenarios each one best suits.

A prime generator set is any standard genset that is used as the primary power source for the equipment it is powering. Generators that are intended for prime operations are designed to run for long periods of time (even 24/7 if required) provided that the load is constantly varying between 50% and 100% of the generator’s prime rating.

For example, our Cummins C110D5 has a prime power rating of 100 kVA. This means that the C110D5 is capable of running for an unlimited number of hours as long as the load varies between 50 and 100 kVA.

In an ideal world, a generator should not be run at below 50% of its rated prime load. This is what’s known in the industry as light or low loading. Low loading should be avoided wherever possible because it can cause the engine to not burn fuel properly. This will lead to a build-up of unburnt fuel and soot in the exhaust which in turn will decrease efficiency and could even damage the generator.

If you own a diesel generator and have been running it at low loads for extended periods of time, then we suggest having your genset load bank tested every year.

Should you need to slightly overload your generator, prime rated generators can be run at their higher standby rating for a short run time, which is typically 1 hour in any 12 hour period. However, the standby rating is the absolute maximum power which can be drawn from a machine.

Examples of Prime Power Use Cases

Prime power products such as diesel generators are best utilised in situations where you are away from a utility source of power such as the mains power from a house or other building.

Examples of this situation would be outdoor festivals or concerts. As outdoor festivals are usually held in remote areas as to not disturb local residents, there is usually no access to mains or grid power. As a result, power must be generated on-site around the clock for the duration of the event. Prime power generators are perfect for this scenario as their ability to run at variable load means that different equipment such as sound systems, lighting etc. can be powered as and when they’re required.

Prime running generators that meet the required emissions standards can also be made mobile by being mounted onto a towable trailer. This makes them much more useful for off-grid power as they can simply be towed to wherever power is needed. If you need a suitable generator to be trailer-mounted

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