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Department of Energy's Question of the Month


Question of the Month: Clean Cities uses a lot of acronyms. What are the most important ones to understand?  


Have you ever been on the DOE’s AFDC to learn about EVSE for EVs or PHEVs to meet EPAct requirements? Let’s take a step back. Perhaps you feel like you need a translator just to understand the basics of alternative fuels and advanced vehicles. If this sounds familiar, get in the know with our list of the top Clean Cities acronyms, broken down into 10 categories:

Federal Agencies and National Laboratories

DOE: U.S. Department of Energy: The federal agency with the mission to ensure America’s security and prosperity by addressing its energy, environmental, and nuclear challenges through transformative science and technology solutions. Clean Cities is part of that overall mission. DOE includes:

EIA: Energy Information Administration: Collects, analyzes, and disseminates impartial energy information to promote sound policymaking, efficient markets, and public understanding of energy.

DOE National Laboratories: Organizations affiliated with DOE, focused on delivering solutions to energy challenges and transforming the way our nation uses energy. There are more than a dozen DOE national laboratories. The labs that contribute to the work of Clean Cities include:

  • ANL: Argonne National Laboratory 
  • INL: Idaho National Laboratory
  • NREL: National Renewable Energy Laboratory
  • ORNL: Oak Ridge National Laboratory
  • PNNL: Pacific Northwest National Laboratory

DOT: U.S. Department of Transportation: A federal agency with the mission to ensure a fast, safe, efficient, accessible, and convenient transportation system that meets our national interests and enhances the quality of life of the American people, today and into the future. The Federal Highway Administration (FHWA) is part of DOT.

EPA: U.S. Environmental Protection Agency: A federal agency with the mission to protect human health and the environment. 


Alternative Fuels Data Center: A web-based resource that provides information, data, and tools to help fleets and other transportation decision makers find ways to reduce petroleum consumption through the use of alternative and renewable fuels, advanced vehicles, and other fuel-saving measures.

Vehicle Characteristics  

GVWR: Gross vehicle weight rating: A metric that includes total vehicle weight plus fluids, passengers, and cargo. GVWR is used to define vehicle classes.

VMT: Vehicle miles traveled: VMT is the number of miles traveled by a vehicle or set of vehicles over a certain time period. 

Fuel Economy 

MPG: Miles per gallon: The standard for tracking a vehicle’s fuel economy.

MPGe: Miles per gallon of gasoline-equivalent: For vehicles that do not use liquid fuels, a measure of fuel economy that allows for a reasonable comparison between vehicles using different fuels. MPGe represents the number of miles the vehicle can go using a quantity of fuel with the same energy content as a gallon of gasoline. 

GGE: Gasoline gallon equivalent: The amount of fuel it takes to equal the energy content of one liquid gallon of gasoline.

DGE: Diesel gallon equivalent: The amount of fuel it takes to equal the energy content of one liquid gallon of diesel. 

Vehicle Classes

Various agencies and organizations classify vehicles differently. Below are FHWA classifications: 

  • LDV: Light-duty vehicle: A vehicle under 10,000 pounds (lbs.; Class 1-2).
  • MDV: Medium-duty vehicle: A vehicle between 10,000 and 26,000 lbs. (Class 3-6). 
  • HDV: Heavy-duty vehicle: A vehicle over 26,000 lbs. (Class 7-8). 

Vehicle Emissions and Pollutants 

GHG: Greenhouse gas: A global pollutant, meaning it has climate and other impacts globally, no matter where it is emitted. Carbon dioxide (CO2) is by far the most abundant GHG produced by the transportation sector.

Air pollutants:

  • CO: Carbon monoxide: A colorless, odorless gas emitted from combustion processes. In the United States, 56% of CO (up to 95% in cities) is emitted by on-road vehicles.
  • NOx: Oxides of nitrogen: A group of highly reactive gasses emitted from combustion processes that contribute to the formation of ground-level ozone.  Approximately 55% of man-made NOx emissions come from motor vehicles.
  • SOx: Oxides of sulfur: A group of highly reactive gasses emitted from combustion processes. SOx is a concern for life cycle analysis of electric vehicle emissions, but not for conventional or other alternative fuel vehicles, because electricity generation is the largest source of SOx.
  • PM: Particulate matter: A complex mixture of acids, organic chemicals, metals, and soil or dust particles, emitted directly from vehicles (especially diesel) and formed through the atmospheric reactions of NOx and SOx. 
  • VOC: Volatile organic compound: Organic compounds that become a gas at room temperature. VOCs are the leading cause of ground-level ozone, also known as smog. 

Alternative Fuels and Alternative Fuel Vehicles 

AFV: Alternative fuel vehicle: Any dedicated, flexible fuel, bi-fuel, or dual-fuel vehicle designed to operate on at least one alternative fuel.


  • B5: 5% biodiesel, 95% petroleum diesel: Considered diesel fuel and approved for safe operation in any compression-ignition engine designed to operate on petroleum diesel.
  • B20: 20% biodiesel, 80% petroleum diesel: The most common biodiesel blend in the United States. 
  • B100: 100% biodiesel: Also referred to as pure biodiesel. 


  • HEV: Hybrid electric vehicle: Powered by an internal combustion engine (ICE) and an electric motor that uses energy stored in a battery. The battery is charged through regenerative braking and by the ICE. 
  • PEV: Plug-in electric vehicle: Derives all or part of their power from electricity supplied by the electric grid. PEVs include: 
  • PHEV: Plug-in hybrid electric vehicle: An HEV that can be plugged into an electric power source to charge the battery. 
  • EV: All-electric vehicle: Uses a battery to store the electric energy that powers the motor. Batteries are charged by plugging the vehicle into an electric power source. 
  • EVSE: Electric vehicle supply equipment: Deliver electrical energy from an electricity source to charge a PEV’s batteries.


  • E85: A high-level ethanol-gasoline blend containing 51%-83% ethanol, depending on geography and season.
  • FFV: Flexible fuel vehicle: A vehicle with an ICE capable of operating on gasoline, E85, or a mixture of the two. 


  • FCEV: Fuel cell electric vehicle: A vehicle that uses electricity to power a motor, but produces its primary electricity using a fuel cell powered by hydrogen.

Natural Gas 

  • CNG: Compressed natural gas
  • LNG: Liquefied natural gas
  • RNG: Renewable natural gas: Also known as biomethane, a fuel produced from organic materials (e.g., waste from landfills, livestock). It can be compressed or liquefied, and is pipeline-quality gas that is compatible with conventional natural gas in vehicles.
  • NGV: Natural gas vehicle: A dedicated, bi-fuel, or dual-fuel vehicle capable of running on CNG or LNG. 


  • LPG: Liquefied petroleum gas: A term used interchangeably with propane.

Clean Cities Tools and Resources 

GREET: Greenhouse gases, Regulated Emissions, and Energy use in Transportation: An ANL model that evaluates the energy and emission impacts of alternative fuels and advanced vehicles, the fuel cycle from wells-to-wheels, and the vehicle cycle through material recovery and vehicle disposal.

AFLEET: Alternative Fuel Life-Cycle Environmental and Economic Transportation: An ANL spreadsheet tool that estimates petroleum use, GHG and air pollutant emissions, and cost of ownership of AFVs and conventional vehicles, using simple spreadsheet inputs. 

PREP: Petroleum Reduction Planning: An online tool that helps fleets create a comprehensive plan to reduce petroleum consumption and GHG emissions. 

VICE: Vehicle and Infrastructure Cash-Flow Evaluation: An NREL spreadsheet model for fleet managers to assess the financial soundness of converting their fleets to run on CNG.

Federal Programs 

CAFE: Corporate Average Fuel Economy: DOT standards to improve the fuel efficiency and emissions of new on-road motor vehicles. 

CMAQ: Congestion Mitigation and Air Quality Improvement: A DOT program that provides funding for projects and programs to reduce transportation-related emissions.

RFS: Renewable Fuel Standard: An EPA program that requires transportation fuel sold in the United States to contain a minimum volume of renewable fuels to reduce GHG emissions. 

RINs: Renewable Identification Numbers: Credits used for compliance with the RFS.

Key Federal Legislation 

CAA: Clean Air Act of 1970: Defines EPA’s responsibilities for protecting and improving air quality. CAA authorizes the development of comprehensive federal and state regulations to limit both stationary and mobile emissions sources. 

EPAct: Energy Policy Act: EPAct 1992 encourages the use of alternative fuels through both regulatory and voluntary activities that DOE carries out. It was amended several times, including via EPAct 2005.

EISA: Energy Independence and Security Act of 2007: Aims to improve vehicle fuel economy and reduce United States dependence on petroleum. EISA includes provisions for the RFS and CAFE standards.

ARRA: American Recovery and Reinvestment Act (Recovery Act) of 2009: Appropriates investments in energy independence and renewable energy technologies, including Clean Cities and other grant programs.


Centralina Council of Governments
9815 David Taylor Drive
Charlotte, NC 28262

Part of the U.S.
DOE Clean Cities
National Network