Understanding Environmental Regulations For Generators: EPA & CARB Compliance

    Posted On: February 3, 2025
    A generator operating on a lawn outside a residence.

    Generators can be lifesavers, keeping hospitals, homes, and other important buildings running during a power outage, but like all internal combustion-powered equipment, they also create air pollution. For this reason, the Environmental Protection Agency has placed regulations on the levels of particulate matter, nitrogen oxides, hydrocarbons, and carbon monoxide that generators can emit to reduce smog and help aid the fight against climate change. 

    In addition to their environmental benefits, EPA-certified generators generally offer such benefits as improved fuel efficiency (so, lower fuel costs), quieter operation, improved safety features, and reliable power output.

    The state of California has created its own far stricter regulations in addition to the national standards set by the EPA to respond to the needs of the state’s environment, where terrain, weather, and large cities combine to create high smog levels. These standards are set by the California Air Resources Board (CARB). As a large producer of an array of food crops and home to many national parks, the state has a vested interest in lowering pollution. 

    About EPA Regulations

    The EPA has released four tiers of regulation for diesel engines since 1994. Tier 1, released in 1994, applied to diesel engines rated at 37 kilowatts or higher. In 2001, the agency enacted Tier 2 to decrease nonroad diesel engine emissions by up to two-thirds. 

    The next reduction came with Tier 3 in 2006, which phased out Tier 2. Stricter engine testing and operation criteria were established by Tier 4 in 2008 and applied to all kilowatt ratings. Tier 4 drastically cut emissions compared to previous standards, with particulate matter emissions that are only one-tenth of those allowed under Tier 3. Tier 5 is currently under development.

    It's important to note that the EPA’s Tier 4F standard makes some exceptions for emergency generators. In the case of an event where a loss of power would cause dire circumstances (such as in a hospital, a 911 call center, etc.), a Tier 2 or Tier 3 generator may be used for standby power only, and some restrictions apply. Visit epa.gov for more information.

    A 2022 Caterpillar XQ60 towable generator parked on an equipment sales lot.
    Caterpillar is a leading manufacturer of EPA-certified, CARB-compliant generators like this XQ60 towable generator set.

    About CARB Regulations

    CARB, founded in 1967 in response to increased air pollution largely attributed to steep increases in automobile use that coincided with a population boom, works to improve air quality and reduce air pollution. In addition to equipment like generators, CARB sets motor vehicle emissions standards and smog check processes for the state and offers financial incentives for clean fuel technologies. The agency’s regulations are generally stricter than those of the EPA. Production, sale, and use of engines (including generators) that are not compliant with CARB regulations are prohibited in the state.

    Several other states have also adopted CARB measures, so it is important to know your local requirements. Colorado, Connecticut, Delaware, Maine, Maryland, Massachusetts, New York, New Jersey, New Mexico, Washington, Pennsylvania, Rhode Island, Oregon, Vermont, and the District of Columbia are among those that have added the stricter regulations. 

    As with the EPA Tier 4 standard, CARB regulations allow for the use of non-compliant generators in the event of natural disasters and other unforeseen events that threaten public health and safety and that fall outside the control of the operator. As with the EPA’s emergency exceptions, restrictions apply, and the owner of a non-compliant device must notify CARB of its operation within 24 hours of its initial use. Visit ww2.arb.ca.gov for more specific information on emergency generator use.

    Meeting The Standards

    In addition to using cleaner-burning fuel like ultra-low sulfur diesel, manufacturers use technological innovations such as diesel particulate filters (DPF), diesel oxidation catalysts (DOC), exhaust gas recirculation (EGR), and selective catalytic reduction (SCR) systems to reduce harmful emissions from the engines.

    Find EPA-Certified & CARB-Compliant Generators For Sale

    Explore PowerSystemsToday.com to find new and used EPA-certified generators for sale from industry-leading manufacturers such as Airman, Atlas Copco, Caterpillar, Cummins, FG Wilson, Generac, Kohler, Multiquip Whisperwatt, Wacker Neuson, and more.

    PowerSystemsToday.com is also a great resource for finding new and used CARB-compliant generators for sale from brands like Airman, Caterpillar, Multiquip Whisperwatt, Honda, Yamaha, and more.

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