When you’re renting a portable generator for industrial, construction or other applications, your options include equipment with Tier 2, Tier 3 or Tier 4 diesel engines. Which type of portable generator should you be using? These Q&As may be helpful to you in making an informed decision.

What is a Tier 4 generator?

A generator with a Tier 4 diesel engine complies with the strict EPA-mandated emissions standards for off-highway diesel engines (rated 56kW or higher) manufactured after 2015. A Tier 4 engine is considered more planet friendly than Tier 2 and Tier 3 engines because it emits considerably less particulate matter (PM) and nitrogen oxides.

Do I have to use a Tier 4 generator for my project?

The rules are different for stationary and portable generators. Stationary generators must have a Tier 4 diesel engine unless they’re used only for emergency backup power.

For portable generators, the answers depends on the geographical location and the project owner. Some state and local governments require the use of Tier 4 generators because they want to reduce emissions and improve the air quality. Others allow the use of generators with Tier 2 and Tier 3 engines.

Today many large corporations, technology firms and other businesses have carbon reduction goals, so they may mandate the use of Tier 4 diesel engine generators on their projects.

In most cases, Tier 2 and Tier 3 diesel generators may be used for backup power in an emergency situation such as an outage due to a hurricane or wildfire.

What are the pros and cons of a portable generator with a Tier 4 engine?

Simply put, a generator with a Tier 4 engine is better for the environment. When you’re running several diesel generators in tandem, the difference is even more significant.

A Tier 4 generator also uses slightly less fuel than a Tier 2 or Tier 3 generator of equivalent power.

To cut emissions even further, some United Rentals customers are now pairing their Tier 4 portable generators with zero-emission POWRBANK portable energy storage systems. These let the user reduce generator run time, which in turn reduces emissions and saves on fuel.

Tier 4 diesel generators tend to be more expensive to rent or purchase, and the technology may feel more complicated to some users. For example, to cut emissions, manufacturers use a selective catalyst reduction system that requires adding diesel exhaust fluid (DEF) to the machine.

Is it difficult to find a Tier 4 generator to rent?

United Rentals understands that customers want to be environmentally responsible, so it has made a point of adding Tier 4 generators, ranging in size from 15 kW to 1.2 MW, to its rental fleet. It currently has more Tier 4 generators than Tier 3 or Tier 2 generators and will likely continue to replace older equipment with Tier 4 generators.

Can I still use Tier 2 and Tier 3 generators on my jobs?

Although manufacturers can no longer produce Tier 2 or Tier 3 portable generators, you can typically use them if the project owner and/or state or local government allows them.

Make sure you’re following any state requirements. For example, the California Air Resources Board (CARB) requires all generators to be permitted, regardless of tier, but does not issue new permits to non-Tier 4 units. United Rentals may be available to help customers with permitting for rented generators.

Are Tier 5 emission standards in the works?

The EPA has not announced plans for a Tier 5 emission standard for off-road diesel engines. However, California’s CARB has started holding hearings for a state Tier 5 standard, and the European Union approved a Tier 5 standard back in 2016.

Since generator manufacturers serve all these markets, Tier 5 diesel engines could become a reality even if the U.S. federal government doesn’t impose a new standard.

How can I determine what portable generators I should be using for my job?

If you or the project owner is committed to reducing emissions, the answer may be to use a Tier 4 generator.

But projects may be complex and budgets may be tight. If lowering emissions isn’t a high priority, talk to the project owner and check with your state and local governments to determine if they require the use of Tier 4 diesel generators or if you can use Tier 2 or Tier 3 models.

Having the right equipment for your project and your budget is paramount. When in doubt, work with a reputable temporary equipment vendor to ensure you rent the right portable generator for your application and situation.

Browse our selection of Tier 4 diesel generators online, call 833.482.3761 or visit your local United Rentals branch to find the portable generator rental you need.