Continuous, Prime or Standby Backup Generator?

When choosing a stationary generator for your business, the first and most important question you need to ask is this: Should I choose a continuous, prime or standby backup generator?

Let's start by looking at the difference between the types:



These gensets operate in a similar way simply because they function as the main source of power, rather than standby power. It follows, then, that they are designed to operate for extended periods of time or even continuously.

The key difference between continuous and prime generators is that continuous gensets, as their name suggests, are designed to operate continuously with a consistent load. Prime generators, on the other hand, are designed to operate for long periods of time with a variable load. It might not sound like much but it's an important difference when investing in a generator for business use.

commercial generators
Pramac build exceptional quality stationary generators for prime and standby power requirements.

Because continuous and prime generators run for long periods of time without a break, they need to be built strong with reliable engines and parts. Robust design is a must to deal with the heavy loads and ongoing heat generation. So it's no surprise that prime generators are more expensive than their counterparts used for standby power.

In Australia, there are many businesses that rely on generators for continuous power. These are typically in remote locations, such as mining, oil and gas, constructions and even ships, where mains power from the grid is either limited or simply not an option.



These units are designed as a power backup in the event of a mains power outage - not for continuous use. In Australia, where storms, cyclones and floods are increasingly common, there's more demand for standby generators than ever before.

Many generators have both ratings for standby power and continuous/prime. Listed in the specifications (typically by kVA) will show you what the generator is capable of depending on the use type. It is advised that if you require a generator for continuous use, you opt for a premium grade genset designed to handle that level of use. When it comes to standby backup generator models, there are more 'budget friendly' options - not to say they aren't still built to high standards, but as they are designed for less frequent use, there are more affordable options that will get the job done.

backup generator
A Powerlink Generator is a good option for standby power; using genuine Perkins Generator is powered by a genuine Perkins, Kubota and Cummins engines.

Continuous/Prime Generator VS. Standby Generator

Cooling systems

One of the most notable features of a continuous/prime generator is the cooling system. Because continuous fuel combustion causes huge amounts of heat to be generated, prime generators typically have a large cooling system for the engine. Generally, cool water is circulated around the engine in a jacket, which absorbs heat from the engine before being cooled by a large-sized radiator fitted with a fan.

Because standby backup generator units typically work for shorter durations, they don't demand the advanced cooling systems and robust, heavy-duty design of continuous and prime generators. They cool down naturally when not in use so only need a smaller cooling system or even an air-cooled system (smaller generators). Powerlink is a good option for a standby backup generator:

PowerLink GMS20KS-AU Diesel Generator Set

Power Output

Because of the different reasons standby generators and prime generators are used, there can be huge differences in their power output. Standby backup generator models can be connected with an automatic transfer switch, enabling them to start automatically when there is a mains outage. The generator then provides varying outputs. On the other hand, continuous and prime generators can provide 25% to 100% of the rated capacity for an unlimited amount of time. These generators can usually provide only constant output at the rated capacity.

Revolution Speeds (RPM)

Continuous generators usually operate at lower revolution speeds, around 1,200 rpm or even 900 rpm, whereas a normal stationary diesel generator will operate at around 1,500 - 1,800 rpm. The advantage of lower revolution speeds is that it lengthens the lifetime of the unit and cuts maintenance costs over the long-term.


A prime generator is usually in continuous operation, which means it isn't possible to clean internal parts and components regularly. To prevent the build up of dust, continuous generators feature heavy-duty air cleaners, air filters and air cleaner assemblies. On the flipside, a big advantage of standby generators is that maintenance can be carried out without disrupting the power supply.

WAIT! Before you buy

Start by making sure you're clear about the purpose of your generator. Is it for standby usage only? Or do you need an uninterrupted supply of backup power for extended periods? Remember to look for the Standby rating and Prime/Continuous rating. This will help you select the right model for your unique needs.


Check out the full range of 3-phase stationary generators and single-phase stationary generators!


DISCLAIMER* Please note, this advice is general in nature and we strongly recommend consulting the product manual and where relevant, a professional installer.

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