Commercial Generator Buying Guide

A commercial generator is a machine that turns mechanical energy into electrical energy and provides power to jobs during outages or sites that are far away from the power grid. Compared to house generators, commercial generators are built with stronger metals, larger engines and larger cooling components. Commercial generators also generate higher wattage outputs than residential generators.

Commercial generators typically cost between $600-$2,000, with many more expensive options for larger jobs and facilities. Prices continue to increase along with the size of generator.

Large generators are suitable for jobs that demand high wattage or a constant rate of flow in one direction. Consider investing in multiple smaller generators if your job calls for the same total wattage spread across multiple locations. Multiple generators at the job site can reduce cordage requirements, limit amperage loss and help the generators last longer.

Generators get larger with the amount of watts they can provide. When looking for the right size generator, consider the total wattage you will need for the job site. There are three types of wattage to keep in mind:

• Running wattage is the standard wattage a piece of equipment uses while running.
• Starting wattage is the extra amount of power your equipment needs to start.
• Surge wattage represents the maximum amount of wattage your generator can produce.

Choose the best commercial generator for your job by calculating your power requirements first. To do this, add the total running wattage of the equipment you need to operate such as a pressure washer or table saw. Then, add that total with your equipment’s single-highest starting wattage. If you do not know the wattage, calculate it by multiplying volts and amps.

Overloading can damage your equipment and the generator. If you do not know the starting wattage of your equipment, you can safely estimate it at 3 times the running wattage. Contractors may want to add 10% to this total to account for error or future power requirements.

Generators found at a job site typically provide 5,000-7,500 watts. These wattages are good for running multiple power tools at a time, such as large table saws, miter saws, belt sanders and grinders.

Some tools may list their power requirements in amps and volts as opposed to watts. Additionally, horsepower (hp) measurements may be used for motor-driven equipment. For example, 1 hp equals 746 watts, and thus a 1/8-hp motor draws 93 watts. Double check the starting power for motor-driven equipment, as it may need nearly four times as much power to start as it does to run.

All power requirements are general examples and should not be used to calculate specific requirements. Always refer to your manufacturer-provided power requirements, which are often found in the user manuals. Also, please note generators should not be used at their maximum capacity for long periods of time. Maintain a usage of no more than 90% capacity. Always place generators in well-ventilated areas.

Commercial generators come with many features to fit different needs on the job site. Select a generator based on the job application and power demands to find the generator with the right features.

Feature categories for commercial generators, as well as their applications, include:

• Multiple outlets for jobs that demand more than a few. Splitters can help increase the number of standard outlets, but a generator with the appropriate amount will be more reliable.
• Outlet configurations vary between generators and can include types like AC, DC and twist locks. Match the NEMA labels on your equipment with the generators’ labels to ensure compatibility.
• Generator fuel options include gasoline, propane, natural gas or diesel, but dual fuel and tri-fuel units are available. Select the option with the most accessible fuel that fits your budget.
• Electric starts help turn generators on easily. These features depend on a battery that may not be included, so it is important to check the requirements. Pull-starts are also available.
• Auto-idle controls increase efficiency by regulating generator engines when they are not in use. This extends run times when jobs require readily available but not constant electricity such as when jackhammering multiple areas of a job site.
• Fuel gauges can benefit your staff by allowing them to check fuel levels visually. Some commercial generators have fuel gauges while others do not.
• Low oil shutdowns turn engines off automatically when their oil drops below minimum required levels. Available on most generators and nearly standard on all standby generators.
• Hour meters track and record a generator’s total running time to can help you efficiently maintain the generator and improve its longevity. For rentals, this can also help gauge if a future purchase is a worthwhile investment.

When measuring the required wattage for your next generator, make a note of all the features your equipment will require. Consider how many outlets you will use at once, what type of fuel will be the most accessible and if you need auto-idle controls. Save these notes along with your wattage requirements and use them to decide on the best generator for your job.

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