The Difference Between Prime & Standby Generators

The Difference Between Prime & Standby Generators

The Difference Between Prime & Standby Generators – There are several factors to consider when choosing the best generator for any application. The generator’s ratings are a good place to start. At its most basic level, ratings serve as a guide to the amount of power a generator is capable of producing. Additionally, they specify how and for what kinds of applications it may be utilized. To ensure that you get a generator that can run your equipment while staying within your budgetary and efficiency limits, it is crucial to comprehend this. The three fundamental sorts of ratings are prime, continuous, and standby. Each of the three will be discussed in more detail, along with when to use each.

Prime Power Generators

A prime generator set is any standard genset that serves as the principal source of power for the equipment it is powering. When the load is continually changing between 50% and 100% of the generator’s prime rating, prime operating generators are built to run for extended periods of time (even 24/7 if necessary).

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A prime power rating of 100 kVA, for instance, on the Cummins C110D5 allows it to run for an infinite number of hours as long as the load fluctuates between 50 kVA (50 percent load) and 100 kVA (100 percent load).

A primary generator is typically used to establish a place that is far from other power sources, such a distant construction site or difficult-to-reach locale. When there is no genuine access to power lines, it functions properly. It can be used as a mobile solution as well. For instance, remote construction sites, oil and gas operations, mines, and rock crushing plants are just a few examples of the applications that use prime power.

The Difference Between Prime & Standby Generators
A Typical Prime Power Generator (Reference:

A generator should never be operated at less than 50% of its rated prime load. This is referred to as light or low loading in the industry. Low loading should be avoided whenever possible because it can result in improper fuel combustion in the engine. As a result, there will be an accumulation of unburned fuel and soot in the exhaust, which will reduce efficiency and possibly even harm the generator.

We advise having your genset load bank tested once a year if you own a diesel generator and have used it at low loads for a long time. If you need to slightly overload your generator, prime rated generators may be run at their higher standby rating for a brief run duration, which is generally 1 hour in any 12 hour period. The absolute maximum power that can be drawn from a machine, though, is its standby rating.


Examples Of Prime Power Use Cases

When you are away from a utility source of power, such as the mains electricity from a house or other building, you should utilize prime power products like diesel generators.

Festivals or outdoor concerts are two instances of this. There is typically no access to mains or grid electricity because outdoor gatherings are typically conducted in isolated locations so as not to bother nearby residents. As a result, electricity must be produced on-site continuously throughout the event. Prime power generators are ideal in this situation since they can operate at a variable load, allowing for the powering of various pieces of equipment like lighting and sound systems as needed.

Prime operating generators that satisfy the necessary emissions requirements may also be made portable by mounting them on a trailer that can be towed. Because they can easily be towed to wherever electricity is required, they become much more valuable for off-grid power. If you require a trailer-mounted generator, please contact Linquip Experts to discuss your specific needs.

Load Management Applications For Prime Power Generators

Prime power generators are frequently used in data centers and power plants as a means to balance the power supplied by utility providers during periods of peak demand. This procedure, known as load management, is profitable for both the utility provider and the end-user.

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Load management often entails a contract between the utility supplier and the end-user — for example, a manufacturing company — to minimize energy use during peak periods by balancing load demand with a prime power producer.

There are two methods you may control your load using your prime power generator:


  • Peak Shaving: The utility company will provide you a certain quantity of power in a peak shaving scenario. Your prime power generator will start up to make up the difference when your application uses more power than that limit. Typically, the utility company will pay the end user for supplying that extra electricity. It aids the utility company in controlling your peak usage periods and forecasting the required amount of grid power.

  • Base Loading: Simply explained, base loading setups are the inverse of peak shaving. Your prime power generator will be set at a preset output. If you need loads that are higher than what your generator can handle, the utility company will cover the difference.

High-consumption applications can use peak shaving and base loading to prevent outages and guarantee that power is always available, even during peak demand periods.


Here are some examples of how load management benefits both the utility supplier and the end user:

By using their primary power generator to generate electricity, the end user—a data center, manufacturing facility, or any other high-usage application—prevents power disruptions and costly downtime. The utility company may reallocate the electricity they don’t supply to the data center and add other customers to the grid without having to build another plant.


Standby Generators

When a power loss occurs, a standby or emergency power generator is put in a fixed location to supply backup power. Although the use cases for prime and standby power differ, the majority of generators may be utilized for either.

The standby rating for generators that can provide both prime and standby power is often higher than the prime rating. This is so that the generator, which can operate at 100% of its prime rating but can also be overloaded up to its standby rating for one hour each 12-hour period. Because standby generators are designed to supply backup power to important equipment and services for a limited amount of time until mains/utility power is restored, they should only be run 1 hour every 12 hours. When mains power is restored to the building, the generator will turn off automatically if it is connected to an Automatic Transfer Switch (ATS Panel).

Due to how easily a storm or other severe weather may create power outages for homes or businesses, backup generators are constantly growing in popularity. They should be sized to average 200–250 hours per year. This makes backup generators very practical in circumstances where a loss of mains power is a possibility. A power outage is not an option for vital institutions like hospitals and data centers. Due to their significance, particularly in industries like healthcare and data centers, they are subject to tight regulations that guarantee they can provide power when needed. NFPA 110 is one of the fundamental standards, albeit it is not the only one. Commercial, residential, and industrial applications are other uses for a standby rated generator set.

The Difference Between Prime & Standby Generators
Standby Power Generators (Reference:

Examples Of Standby Power Use Cases

An automated backup electrical system is known as a standby generator. An automated transfer switch detects the power loss immediately after a utility outage, starts the generator, and then switches the electrical load to the generator. The backup generator starts powering the circuits. The automated transfer switch transfers the electrical load back to the utility once utility power is restored and tells the backup generator to shut down. It then goes back into standby mode and waits for the next power loss. A backup generator does weekly self-tests to make certain that it will react to an outage properly. Most appliances use diesel, natural gas, or liquid propane gas as fuel.

For important safety systems like elevators in tall buildings, fire protection systems, backup lighting, or medical and life support equipment, building rules may impose requirements for automatic standby generator systems. Residential standby generators, which supply backup electrical power to home equipment like refrigerators, stoves, and water heaters as well as security and HVAC systems, are becoming more and more popular.

Continuous Generators

A continuous generator is one that is employed similarly to the primary source of power. It is typically made to operate as the facility or function’s main source of electricity on a constant basis. A continuous generator and a prime generator vary in that a continuous generator does not provide variable power. Instead, it is intended to deliver a constant power load for the duration of its use.

The greatest use of a continuous generator can be found in many different circumstances. Most of the time, it works well when other power sources are not available or economical, such as when installing power at a specific remote location is necessary but running power lines is not economical. They are also advantageous to utilize when the power supply is otherwise too unreliable.

These generators are critical instruments for remote areas since they continuously produce electricity at full load capacity. They simply cannot provide flexible capacity like prime systems. They are frequently employed in mining, the military, and agriculture, but they can also be useful in a wide range of other applications.


Difference Between Prime Power And Standby Power

The following points highlight the primary distinctions between prime and standby generators:

Intended Use: While Standby Power (emergency power) is to be used in the event that the primary source of power fails, Prime Power is the primary (main) source of power on the site. When the Grid (mains) experiences a power outage, or a power cut, standby generators are used primarily as backup power.

Generator Load: Prime power is defined as unlimited hours at a variable load, whilst standby power can be variable or constant load.

Run Time: Standby generators are only intended to be run 1 hour in 12, while the prime power ratings can be defined as having an unlimited run time.

kVA Rating: The standby rating is typically higher than the prime rating.

Application: Prime power is suitable for situations where mains power is inaccessible, whilst the standby power is an emergency power during a power outage.

The manufacturer’s warranty changes according to the kind of operation, which is another aspect to take into account when comparing prime and standby generators. For instance, the Cummins generators’ manufacturer warranties are 2 years or 500 hours for standby use and 1 year unlimited hours for situations requiring prime running.

The Difference Between Prime & Standby Generators
Preventive Maintenance Program Is Essential To Ensure Reliability Of All Power Generation Equipment. (Reference:


Key Considerations to Think About When Purchasing a Generator 

Always choose a personalized solution. Because of this, it is crucial to think carefully about every component of your generator before making a purchase. You don’t have to purchase the most expensive model, but you do need one that meets your operating demands. Consider choosing the correct generator as more than just a financial choice.

Decisions like whether access to gas or diesel power is available are among the things that need to be taken into account. A single-phase or three-phase system can be required. Determining the generator’s intended use, whether it will serve as the main source of electricity or a backup in case of emergencies, is equally crucial. What parts make up a generator set? Not every requirement can be met by a common solution.

Consider the following factors when choosing the best generator for your requirements: site circumstances and applications, peak and continuous demand, and duty cycle (number of hours per day per week per year).


FAQs about The Difference Between Prime & Standby Generators


  • How Much Time Can A Standby Generator Run Constantly?

A standby generator can often power a medium-sized home for up to 3,000 hours, while it is recommended that you do not operate a generator for more than 500 hours continually.


  • Who Manufactures The Greatest Home Standby Generator?

The 5 top whole house generators in august 2022 is:

  • Generac Guardian Wi-Fi Enabled Standby Generator.
  • Briggs & Stratton 12,000-Watt Automatic Air Cooled Standby Generator.
  • Champion 14-kW aXis Home Standby Generator with 200-Amp Whole House Switch.
  • Generac PowerPact 7,500 Watt Standby Generator.
  • Generac Guardian 3-phase 20kW Automatic Standby Generator Wi-Fi Enabled.

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