How to Choose the Right Size and Type of Commercial Generator for Your Business

The U.S. electric grid is aging. Despite promises of upgrades and improvements, little has so far been done.

You can take action to protect your business from the significant negative consequences of power outages. A commercial generator gives you assurance that you can continue to operate, even during a blackout.

Choosing the right generator type is very important, as you’ll need a model that’s the right size and meets your operating requirements.

Learn more about how to choose the right generator size and what else to look for in a commercial generator.

Categories of Generators

Before you can calculate the generator size you need, you need to determine how you plan to use the generator. Then you’ll be able to decide which category of generator will be best. Choosing the right category depends on what you want the generator to power.

Emergency Generators

An emergency generator powers your essential system during a blackout. It can temporarily support emergency lights, fire alarms, and other systems necessary for an evacuation.

Standby Generators

A standby generator will power your entire facility during a power outage. You can install it so it turns on automatically when a blackout occurs. This type of generator kicks in rapidly, so disruption is minimal.

Primary Generators

A primary generator serves as your main power source. This is a good choice if your site is too far away from the power grid or if the local grid doesn’t produce enough electricity.

How to Estimate the Generator Size You Need

You can use one of several methods to estimate the generator capacity you need. The best method depends on the type of commercial application you have.

Square Footage Sizing

Estimating generator size using square footage is very simple. It works best for retail and commercial applications like grocery stores, restaurants, and convenience stores.

For retail applications, use 50 kilowatts plus 10 watts per square foot. For other commercial applications, use 50 kilowatts plus 5 watts per square foot.

Full Load Capacity by History

Another relatively straightforward method is to look at your past energy use. This is a good method for facilities with equipment that operates continuously, like freezers or refrigerators.

Look at your utility bills for the past year. Most energy companies include your peak demand on your bill. Find the highest peak demand in the last year and add 25% to account for reserve capacity.

Full Load Capacity by Measurement

You can calculate how much generator capacity you’ll need by measuring your peak energy use. This method requires more calculations.

First, take a full-load current measurement during peak demand at the service panel. You can get this number by using a clamp-on ammeter on each leg of the electrical service and adding the measurements together.

Second, divide the total amps by three for three-phase current or two for single-phase current. Multiply the result by the supply voltage. Divide that result by 1,000 to convert it to kilowatts.

Third, add the power in kilowatts that each of your emergency safety systems uses. This gives you the full load in kilowatts.

The next step is to calculate the reserve capacity. Multiply the full load by 0.25. Add the reserve capacity to the full load to get the total capacity you need for your commercial generator.

Full Load Capacity with Extensive Motor Use

If you need a commercial generator that can handle extensive motor use, you may want to calculate the capacity based on the watts required for each load.

First, find the starting current for the largest motor that turns on and off. Multiply the current by the voltage to find the watts. Next, multiply the current by the voltage for all other loads.

To find the full load in kilowatts, add the watts of all loads and divide the total by 1,000. Multiply the full load by 0.25 to find the reserve capacity. Add the reserve to the full load to find the generator size you need.

Types of Generator Fuel

The most common types of fuel for commercial generators are diesel, natural gas, and propane. Each type has pros and cons for backup power.

Diesel

Diesel generators are very popular. Diesel engines are reliable and durable, and you can get diesel fuel easily.

A diesel generator is often the least expensive to run and maintain. However, the shelf life of diesel may be as short as 12 months. Careful planning for delivery and storage is important.

Natural Gas

Natural gas is widely available in cities and towns through the utility grid. It is delivered directly to you through a pipeline. It doesn’t require refueling or storage on-site.

However, natural gas has a lower power output and a higher consumption rate than other fuels.

Propane

Propane is easy to store. It has an unlimited shelf life.

However, the fuel system to burn propane is complex. The installation and maintenance can be more expensive. Propane is usually a more expensive fuel as well.

Choosing a New vs Used Generator

You have the option of a new or used generator. The obvious benefit of a new generator is you get it straight from the factory in perfect working order. You don’t need to worry about whether the previous owner maintained the generator properly.

However, you can save a significant amount of money by choosing a preowned generator. Working with a reputable dealer is essential. They will examine and test the generator so you have an accurate assessment of its condition.

A quality dealer will stand behind the used generators they sell, giving you peace of mind.

Find the Right Commercial Generator for Your Business

A commercial generator is essential for the safety of your business and your ability to operate. Choosing the right generator size helps ensure you get the best performance and the most benefits.

Swift Equipment Solutions specializes in commercial generators. We take time to understand your needs and recommend the best solution.

You can save money with our refurbished models. We thoroughly inspect, service, and test every used generator so you know it’s in the best possible condition.

Reach out to Swift Equipment today to discuss the generator size you need, and we’ll find you the right backup power solution at the right price.