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Dispelling Generator Misconceptions

Generators, despite what some might think, are not plug and play. It’s true that most manufacturers follow international rating standards as it pertains to a generator’s performance parameters.

Small variations by manufacturers, however, can cause confusion and ultimately an underperforming generator. These three areas need to be carefully understood as you consider your next generator purchase.

Gross power output versus net power output

A generator’s gross power output refers to the maximum amount of power that is available from the genset without factoring in the electrical power it uses during operation.

The net power rating refers to the maximum amount of power that is available from the genset after subtracting the electrical power it uses during operation.

For example, if a genset has a gross power rating of 3,100kw and the cooling package uses 100kW to power the cooling fan, then the genset’s net power is 3,000kW.

Understanding the definition of both terms and how they interact is key to determining your true power needs and if the genset you’re considering will be able to meet those demands.

Load factor

The average load factor of a generator set is determined by measuring its performance during a 24-period. Engineers at the design stage study a facility load profile and determine the generator size based on the maximum demand and on the average predicted loading a genset would need to handle.

If you think about it, the energy usage of a building is going to vary throughout the day. It will be heavier during normal business hours as lights, computers and air conditioning need are the greatest. Conversely energy usage will taper off as workers go home.

International standards require that manufacturers design gensets to meet an average load factor of 70 percent. MTU gensets, however, are designed to operate at an average daily load of 85 percent. Customers effectively get 15 percent more average loading out of MTU Onsite Energy systems compared to the competition.

One final point of consideration in determining the right genset for your needs is consideration of future expansion possibilities to ensure you’re purchasing the correct unit size.

Maximum run time

The maximum run time under international standards are determined under test conditions for generators. So how does that translate to a generator’s operation during a long-term outage? You, unfortunately, won’t get a uniform answer. Manufacturers do their best to make estimates.

MTU, for example, sets a maximum run time of 500 hours annually, compared to 50 to 200 hours from competitors. Go beyond that and some manufacturers have internal governors that will shut the unit down. MTU units will continue to operate with the only repercussion being a standard maintenance visit coming sooner rather than later.

Understanding these four key areas of a generator’s capabilities will greatly help in choosing a unit that fits your needs and operates cost effectively. Pacific Power Group has the experience with MTU units across a broad range of markets to assist in your generator selection. Let us know how we can help.