What Will Your Generator Derate Be and Why?

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Before you purchase a generator, it’s essential to calculate the size you need, expressed in watts of power, by tallying up the needs of the equipment that will run on it. This size calculation includes the maximum watts required for all equipment to start and run at peak power. After sizing a generator and buying one based on this figure, you’d expect everything to run on it without a problem, but generator derate can get in the way.

What is generator derate, and how can you mitigate it to get the most power from your backup source of electricity? In this blog post, we’ll explore generator derate and explain what can cause your generator to perform less powerfully. We’ll also discuss adjusting surroundings and fuel types to get the most out of your backup power source.

Derate Defined

According to the U.S. Energy Information Administration, derate refers to a temporary decrease in generator capacity due to system changes, equipment modification, operational differences, or environmental factors. Unless the deration occurs due to a generator modification, transient conditions typically cause the problem. In some cases, a generator operator may derate the generator to extend the life of the engine, which also reduces the generator’s power output.

Factors Causing Deration of a Generator

Aside from mechanical modification of a generator, equipment age and environmental factors top the list of causes for generator deration. Let’s consider the specific environmental causes that the Electrical Engineering Portal says can temporarily or permanently affect your generator’s capacity:

  • High cooling water temperature
  • Altitude
  • Dust
  • Humidity
  • Corrosive atmosphere

Of all corrosive elements, salt damages generators most frequently and can permanently damage components. For example, humid, salty air, such as that found in a seaside area, can cause corrosive damage to the winding insulation the protective layer around the coils inside the generator which can lead to device failure.

Generator Derate and Altitude

Changing environmental factors make it challenging to adjust your generator output rating calculation so you can accurately plan which equipment you can operate. However, altitude is a constant that you can plan on using a standard derating formula. For every 1,000 feet increase in altitude, a generator loses about 4% capacity.

Generator Derate and Temperature

Ambient temperature significantly affects engine output. Developers design engines to operate within specific parameters, including an ambient temperature range. When the temperature rises above the engine’s ideal operating conditions, it causes a derate. A 10-degree difference from optimum conditions can reduce power by 5% to 10%. Operating a generator in overly cold conditions also causes less than optimum performance.

Fortunately, you can control the temperature under which your generator operates. Use temperature control products to extract heat from the engine’s cooling system. If the generator runs in overly warm conditions, it reduces engine performance and uses more fuel.

Protecting a Generator from Environmental Conditions

Although environmental factors in power generation can affect your generator capacity, simple mitigation methods can ensure a reliable generator load. One strategy is to build an enclosure to protect your generator from corrosive elements as well as conductive and abrasive dust.

Construct an enclosure that’s large enough to accommodate a space heater or dehumidifier. Maintaining an ideal humidity level will protect the generator from moisture-related issues. For example, if you’re using a space heater to dry the air in cold, damp weather, maintain a temperature of at least 41F (5C) without exceeding 104F (40C). This is the generally accepted safe operating temperature range for most generators. However, ideal temperature ranges may vary, so check the requirements for your generator model to ensure it operates efficiently and safely.

Choosing an Alternative Fuel

Many of today’s generators operate on more than one fuel. Using the recommended generator fuel choices can maximize output, even in less-than-perfect conditions. Dual fuel generators offer versatility. Although diesel generators typically provide the most efficient operation, a generator that can operate on more than one type of fuel can help you avoid diesel engine derating. That’s because fuels differ in their derating factors. For example, natural gas generators have a 5% derate factor, but liquid propane has a derate factor of 2% to 3%, depending on elevation.

Manufacturers of multiple fuel generators note the optimum operating conditions using each fuel. Check your generator’s owner manual to determine which fuel type is best under the conditions you’ll need to operate the machine.

Getting the Most Out of Your Generator

A derated engine operates at less than optimum capacity. While you can’t always control external factors that lead to less-than-ideal operating conditions, you can take steps to minimize the impact.

Before you buy a new generator, contact us for a consultation. We’ll work with you to evaluate the impact of your pending purchase and help you choose a generator that meets or exceeds your specifications. Let our engineering support team help you choose the right device and devise methods to maximize capacity. Don’t go it alone. Let our experts help you select a generator designed to operate in your typical conditions and provide the maximum watts you need.