How to Size a Generator for a Commercial or Industrial Building

If you’ve ever purchased a generator before, you already know how complicated it can be – generators come in all shapes and sizes, and are able to meet a long list of uses. And while you might be familiar with how to use a home generator, or hooking up a portable generator, choosing the right generator for a commercial building is a different story.

At Buckeye Power Sales, our professionals have been helping our customers find the right tool for the job for over seven decades, and selecting a generator is no exception.

We’re happy to work with you to choose the right generator for your commercial needs. But building a good understanding of their capabilities beforehand will save you time, effort, and resources. Here’s what you need to know.

What Makes a Commercial Generator Different than a Residential Generator?

Not all generators are created equal. Generators used as backup, or standby power for a typical home are generally smaller, portable, and can cope with the light-to-moderate power needs that your home would demand.

Commercial generators, on the other hand, are designed to fully power a business or commercial site during loss of power, and to run continuously and indefinitely until that power is restored.

They include automatic operation, meaning that the generators engage automatically when the power goes out, and shut down when it returns. This ensures there are minimal gaps in which your computers, refrigerators, engines, etc., will stop running.

Also different from residential generators, commercial generators usually include an automatic voltage regulator, which ensures continuously-controlled voltage (preventing surges and dips in power that can damage equipment or stall operations).

Determining What Size Generator You Need

Choosing the right size generator to suit your needs is the most important part of your decision. Underestimating your power needs can not only slow or stop your operation – it can damage important equipment.

We’ve put together a handy information sheet to walk you through all of the details, which we recommend you download and read. But in the meantime, here are a few of the critical factors that go into your decision.

Voltage Dip

Different pieces of equipment have different tolerances for voltage dip, and the starting load of an electric motor can be as much as six times its running load.

Since that starting load can affect your generator’s regulator system by reducing the available voltage, you need a generator large enough to handle the maximum allowable voltage drop. You’ll need to consult the manufacturer’s spec sheet for your equipment to determine what the allowable drop in input voltage is.

Frequency Dip

Generators have a nominal frequency (60Hz in North America). But, extremely heavy loads, especially on start up, can reduce engine speed, affecting that frequency. The maximum transient drop in speed and frequency of what the system can handle both need to be taken into account.

Ambients

Any combustion engine requires a certain amount of air to function properly. Your altitude, humidity, and temperature range will all affect how well (or poorly) your generator operates.

Generator manufacturers provide guidelines for what percentage of power reduction you can expect when ambient conditions exceed the nominal rating.

Application

Generators come in either prime or standby. Your commercial application will determine your backup power needs: whether you require continuous operation from generator power, or if you need only temporary coverage during main power interruption.

How We Can Help

Knowing when to ask for help is key to any large enterprise, and ensuring your business has continuous power coverage is no exception.

Large operations typically require an engineering plan be drafted for your commercial generator selection, and your engineer’s supervision during the install. Start by working with your own staff, or contracting a professional engineering firm, to make sure you understand your system’s needs and comply with regulations.

Once you’ve assessed your system’s needs, our pros can walk you through which products will make the best fit for your business.
You can view more about the generators we offer here on our website, and make sure to reference our extended generator sizing information sheet as a reference. With the right knowledge ahead of time, keeping production up and running during the next power outage will be no problem.

Download our Generator Sizing Guide