What are the Generator EPA Tier Ratings?

The U.S. government produced a set of regulations and guidelines to strategically reduce harmful emissions and release of pollutants into the atmosphere to improve the overall air quality. These regulations put a limit on exhaust emissions for non-road diesel engines, which ended up regulating the very generators that we rely on today. Over time, these regulations became stricter and enforced greater control and requirements that generator manufacturers must adhere to and are regulated by the Environmental Protection Agency (EPA).

These regulations were not carried out overnight, but were rolled out in phases. This provided manufacturers time to develop new technology that adheres to the EPA rules & regulations of emissions, while mitigating any negative impact to the overall business. Each phase of regulations was assigned within a rating system by tiers and correlated to an engine’s horsepower rating. As each phase rolled out and went into effect, limitations on Carbon Monoxide (CO), Hydrocarbons (HC), Diesel Particulate Matter (DPM), and Nitrogen Oxides (NOx) became increasingly stricter.

The Tiers are Tier I (Tier 1), Tier II (Tier 2), Tier III (Tier 3), and Tier IV (Tier 4) respectively.

Tier 1 – Focused on diesel engines for vehicles and phased in from 1994 to 1997

Tier 2 – Enforced stricter regulations of Nitrogen Oxides (NOx), Hydrocarbons (HC), Diesel Particulate Matter (DPM), and Nitrogen Oxides (NOx) emitted and was phased in from 2000 to 2005. Phasing in Tier 2 also defined restrictions for the amount of sulfur allowed in gasoline and diesel fuel, since sulfur can interfere with the operation of advanced exhaust treatment systems, such as selective catalytic converts and particulate filters.

Tier 3 – Restricted exhaust emissions for engines ranging from 50 to 750 horsepower (hp) and phased in from 2006 to 2008, with a requirement that all new diesel generators were to be in compliance starting 2007.

Tier 4 – Is the strictest regulations standard that requires a 90% reduction of Diesel Particulate Matter (DPM) and Nitrogen Oxides (NOx) emissions with reductions made possible through newer control technologies and was phased in from 2008 to 2015.

Emergency Generator Standards

When it comes to EPA Tier regulations and standards, emission standards for backup emergency generators differ from non-emergency generator standards, such as prime or continuous generators. If you have a backup generator installed or are looking to install a backup generator in the case of emergencies, emergency generators are generally only subject to EPA Tier 2 and Tier 3 regulations and not Tier 4 regulations. The basis is that these backup emergency generators are only used temporarily in case of emergencies and therefore do not have to adhere to these stricter Tier 4 regulations, as long as they are in compliance with Tier 2 or Tier 3 regulations. The reasoning is due to the fact that Tier 2 and Tier 3 generator engines already exhibit adequate reductions in emissions, run between 200 to 500 hours per year, and the emissions produced by Tier 2 and Tier 3 generators have a low impact on local air quality.

It’s important to note that though backup emergency generators are federally exempt from EPA Tier 4 regulation standards, authorities within your state or local municipality can enforce strict regulations or guidelines that you must adhere to. For example, the state of California may require you to be in compliance with EPA Tier 4 regulations or CARB compliance (if using a natural gas generator).

Emission Upgrades

If your generator fails to meet certain EPA standards, there is an option available aside from replacing the generator entirely, such as a generator emission upgrade. The upgrade is essentially an aftermarket attachment that is installed on the generator called a diesel oxidation catalyst (or DOC for short).

The diesel oxidation catalyst (DOC) is designed to oxidize carbon monoxide (CO), gas phase hydrocarbons (HC), and diesel particulate matter (DPM). What it does is it converts carbon monoxide (CO) and hydrocarbons (HC) into carbon dioxide (CO2) and water vapor. This results in less harmful emissions released into the atmosphere.

This upgrade reduces carbon monoxide (CO) by up to 99%, hydrocarbons (HC) by up to 90%, diesel particulate matter (DPM) by up to 95%, and nitrogen oxides (NOx) by up to 99%.

It should be noted that not all commercial generators will automatically become compliant with EPA Tier 4 standards and regulations with an upgrade, but it may be a sound solution worth looking into if you’re looking to get your current generator in compliance with EPA Tier 2 or Tier 3 standards.

More information on generator emission upgrades can be found here: Generator Emissions Upgrades

What Has to Adhere to EPA Tier 4?

There are quite a few generator applications that must be in compliance with EPA Tier 4, but the most common are the following:

Prime Power Generators

Prime power generators are used as a primary power source for power needs when disconnected from or working off the main power grid and runs continuously to provide power for key equipment and machinery. Due to this fact, these generators are not considered emergency generators and must adhere to EPA Tier 4 regulations.

Portable Generators

Portable or mobile generators used for specific applications are required to adhere to EPA Tier 4 regulations, especially when used for commercial or industrial applications, such as construction projects off the main power grid, events off the main power grid, or peak shaving.

Management & Incentive Programs

Generators used in load management, peak shaving, or demand response incentives are subject to EPA Tier 4 regulations and include any generator sets that are paralleled with the local utility and used for these applications. While generators used for these applications are technically also able to be used for emergencies, the capability of load management disqualifies these generators from Tier 4 regulations.

If you’re looking for more information or consultation on EPA Tier requirements for generators, generator emissions upgrades, or applications that must adhere to EPA Tier 4 regulations, please reach out to us at Woodstock Power Company!



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