When electrical connections are limited or non-existent at a jobsite, a portable generator keeps the power tools running and your workers productive. Portable generators also are handy for emergency or standby power.

There are several factors to consider when choosing a portable generator, including the total wattage you’ll need, the optimal fuel source, the decibel rating and features that will make using the generator easier or more efficient.  

Here are some tips to help you select a generator for your job. 

Get the power you need

Portable generators come in a variety of sizes and power options, ranging from 2.0 kW to 10-plus kW. To determine the size you need, add up the total running wattage of all the power tools you plan to operate from the generator at the same time. If you’ll be using two drills or three belt sanders, figure in the wattage required for each one. 

Add in the highest starting (surge) wattage of all the tools. (Some power tools require a lot more power in the first two to three seconds after they start.) Since most tools won’t start at the exact same time, you need to include only the highest starting wattage, not the starting wattage for each tool. 

Check the brand and model of the equipment you’re using to determine your actual power needs.

One last power consideration: Don’t forget to count the outlets on the generator so you’ll have enough places to plug in all of the tools you want to operate at the same time.

Fuel options

Portable generators on construction sites generally run on gasoline, diesel or propane.  There are advantages and disadvantages to each. Consider the cost and availability of the fuel types, as well as the size of the fuel tank. More-frequent refills equal more downtime on the job.

• Gasoline is readily available, but storing it in large quantities can be dangerous because it is highly flammable. If there’s a widespread power outage, you’ll have trouble getting the fuel you need since fuel pumps require electricity to operate.  Gasoline engines aren’t as clean burning as diesel; so, gasoline-powered generators may require more frequent servicing.
• Diesel fuel is less flammable than gasoline or propane and is also the most fuel-efficient and least expensive choice. Diesel generators generally run longer without maintenance than gasoline-powered generators. But like gasoline, diesel fuel may be difficult to obtain if the power goes out, and diesel generators are often louder than gas or propane models.
• Propane is the cleanest burning but least efficient fuel. Propane generators are generally the quietest, but they may need more frequent servicing. Propane fuel is easier to store in large tanks, which means less refilling, but the fuel is highly flammable if the tanks are punctured. 

Some portable generators are now available in dual fuel (gasoline and propane) or even tri-fuel (propane gas, natural gas or gasoline) options.

Decibel ratings 

Generators can be very loud; so, look for a unit with a low decibel rating, particularly if you’ll be using it near workers. It’s especially important to choose a quiet generator if it will be used near workers in a confined space. Some generators at the lower end of the wattage spectrum are rated as low as 57 decibels at 100 percent load. 

Quieter than conventional generators are silenced generators, which are enclosed in an acoustic cabinet. Quieter still, and more expensive, are inverter generators. These convert AC power to DC power before digitally “inverting” it back to cleaner AC power.

RELATED: Reducing Noise on the Jobsite 

Desirable features

Features that help you get the job done faster with less effort may be worth the investment. Here are a few to consider. 

• Professional grade. If you’re planning to use a generator long term, look for a unit that’s built for everyday duty and not just occasional use. Portable generators that are ideal for homeowners dealing with a temporary power outage may not stand up to the demands of a jobsite. Thick-gauge steel construction and a large fuel tank can be an indication that the generator is meant for heavier-duty use.
• Electric start. Want a fast start to your workday? Look for a generator with an electric start option.
• Wheels and handles. If you’ll be moving the generator around to different areas of the site, no-flat wheels and collapsing transporting handles that stay out of the way when you’re using the generator are useful features. 
• Tier 4 engine. If you’re planning to rent a diesel generator, look for one that meets the EPA’s Tier 4 emissions standards. Compared to previous models, these diesel generators reduce the amount of nitrous oxide, particulate matter and hydrocarbons released into the atmosphere. 

Other handy features to look for include idle control, covered outlets and full-panel GFCI protection. 

United Rentals can assist you in selecting a portable generator for your next project.  Simply contact a United Rentals sales representative at a branch near you or call 1-833-451-5765.

Freelance writer Mary Lou Jay writes about business and technical developments in a variety of industries. She has been covering residential and commercial construction for more than 25 years.