Santa Barbara County Air Pollution Control District

Clean-Air Vehicles Overview and Links 

A Clean-Air Car Primer

Note:  to compare vehicles by fuel economy, fuel types, and emissions, see California Air Resources Board Drive Clean California and the EPA Green Vehicle Guide.

ZEVs are zero-emission vehicles, the cleanest you can find. The only ZEVs are electric vehicles, and some fuel cell vehicles (not available to consumers for several years). It's difficult for a consumer to purchase a new electric vehicle at this point, as there are not many on the market.

PZEVs are partial zero-emission vehicles, the closest you can get to zero without being a ZEV. The partial refers to the fact that automakers get partial ZEV credit for making and selling PZEVs. They're cleaner than SULEVs since they also have a design that doesn't allow evaporative emissions from the gas tank. There are PZEV versions of several new gasoline car models on the market today. To see a list of these, visit the California Air Resources Board link in the list below.

AT PZEVs are PZEVs that have an advanced-technology component, such as a hybrid system.

SULEVs are super-ultra low-emission vehicles, extremely clean.  There are both gas SULEVs and gas-electric hybrid SULEVs on the market today. The  classifications of ZEV, PZEV, or SULEV only refer to the air emissions, by the way -- not the fuel efficiency. The EPA Green Vehicle Guide in the link below will allow you to look up vehicles and compare both emission and fuel efficiency characteristics. Remember that 2005 and 2006 trucks and Sport Utility Vehicles do not have the same standards and ratings as cars, so a SULEV Sport Utility Vehicle can pollute much more than a SULEV car.

ULEVs are ultra low-emission vehicles, somewhere between a SULEV and a LEV (low-emission vehicle). The current requirements for new model cars are so close to the LEV classification that many new car models are already LEVs or ULEVs.

LEV II refers to standards that were set by the California Air Resources Board, to tighten emissions standards overall, and to extend the more stringent passenger-car standards to light-duty trucks and SUVs. 

Gas-Electric Hybrid vehicles, also known as hybrid electric vehicles, are vehicles that have both a gasoline engine and fuel tank, AND an electric motor and battery. These vehicles have better fuel efficiency and produce less air pollution than many conventional gas-powered vehicles. Hybrids are refueled with gasoline; the batteries are recharged automatically as the vehicle is moving.  There has been a $2,000 federal income tax deduction applying  to purchase of hybrid vehicles on the market, check with the Internal Revenue Service or with automakers (for example, on this site:

Fuel Cell Vehicles are electric vehicles in which the power is provided by an onboard fuel cell, which creates electricity through chemical reactions involving hydrogen. There are several different designs in development. In some, the vehicle has a hydrogen tank and is refueled with hydrogen. In others, the vehicle has an onboard reformer that extracts hydrogen from some other fuel (typically methanol, gasoline, or natural gas).  The fuel cell process creates almost no air pollution; however some pollution is associated with the extraction, storage and delivery of hydrogen. Many automakers are developing fuel cell vehicles, for more information, see the California Fuel Cell Partnership.

Hydrogen-powered internal combustion engine (ICE) vehicles have ICE engines that burn hydrogen (which burns very cleanly, producing very little pollution). BMW is one automaker that is developing ICE vehicles that can run on either gasoline or hydrogen.

Compressed natural gas (CNG) vehicles are ICE vehicles that burn compressed natural gas (which burns cleanly). Some commercial vehicles in Santa Barbara County use CNG. However, there is only one public CNG refueling station in the county, and due to technical issues around the composition of the natural gas in this area, consumers are not able to refuel with CNG at their homes.

Biodiesel vehicles are vehicles with diesel engines that burn biodiesel. The term "biodiesel" is used to refer to a variety of different substances: a fuel that is 100 percent "virgin" vegetable oil, often soy oil; a fuel that is 100 percent recycled vegetable oil (often recycled from restaurant use); and a fuel that is up to 80 percent petroleum diesel and 20 percent vegetable oil. The emissions from biodiesel vehicles can vary a lot, depending on the type of vehicle and fuel's composition, and whether or not there are any emission controls installed on the vehicle. From an air pollution standpoint, a PZEV, SULEV or ULEV gas or hybrid vehicle will run much cleaner than an older diesel vehicle without advanced emission controls burning a "biodiesel" blend that is actually 80 percent petroleum diesel. However, there are renewable energy and other advantages to use of 100 percent biodiesel. 


There are many websites with information on clean-air vehicles, and refueling alternate-fuel vehicles; just a few are listed below. It's also good to check out the auto manufacturer's website for more information on a specific vehicle.

EPA Green Vehicle Guide

California Energy Commission Transportation Choices

California Air Resources Board Drive Clean CA

Clean Car Maps

California Fuel Cell Partnership

WestStart-CALSTART Advanced Transportation News and Information

Department of Energy Fuel Economy Guide

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