Five Reasons Why Your Generator kW Rating Is Inaccurate

kW Rating Graphic

1. Compression Ratio

Compression Ratio directly affects the kW output of a generator set. Most manufacturers build their engines with a high compression ratio in order to get the highest level of output from a generator. This works great when the generator is running off of 100% methane or pipeline quality gas. However, in the Oil & Gas industry, wellhead gas is almost never close enough to pipeline quality gas to not incur some sort of derate in kW. Depending on the wellhead gas composition, derates can vary from 5% all the way to 75%, or even make the generator inoperable. A solution for this is low compression pistons, as they can help alleviate much, if not all of the derate potential.

2. Standby, Prime, and Continuous Rating

In the power generation industry, particularly in the rental equipment sector, standby, prime, and continuous ratings are often blurred in order to offer a higher perceived value. This is reflected in a falsely inflated kW rating offered at a lower cost. This is an important factor to consider when sourcing for prime or continuous applications because the standby rating is often what is presented or advertised. It should be noted that for a given generator, the standby rating is between 10% – 25% higher than the prime or continuous rating.

3. Altitude

Generator engine design varies by manufacturer, and can significantly affect how a generator will run at higher altitudes. For example, derates in kW can range from 0% – 40% at 5000 feet altitude, depending on the manufacturer. Whether a generator is naturally aspirated or turbo-charged also has a great impact on altitude deration. Be sure to review and understand the derate information of the specific generator, prior to making your purchase or rental decision.

4. Temperature

The on-site temperature where the generator will be used is an important factor in determining kW derate. Higher operating temperatures can lead to a generator engine overheating. To avoid engine overheating, the load put on the generator will have to be reduced, effectively reducing the kW rating.

5. Parasitic Loads

It is common practice for companies and manufacturers to exclude parasitic loads in their kW rating. However, a parasitic load such as a radiator can negatively affect the kW rating of a generator by as much as 20%. It is important to account for all parasitic loads to get an accurate kW rating.

Contact Global Power Supply today to get expert assistance in properly purchasing or renting by kW rating.