History of California's Zero Emission Vehicle (ZEV) Program

California's Zero Emission Vehicle (ZEV) program requires auto companies to produce a certain percentage of zero emission vehicles for sale in California, such as hydrogen fuel cell, battery electric, and hybrid vehicles.

The California Air Resources Board (CARB) is in charge of the ZEV program, and typically updates it every three years. The ZEV program has a short, yet complex history, and contrary to popular belief, the regulation is not dead, just modified from its original form. 

Here come the electric cars!

As first enacted in 1990, the ZEV regulation required that two percent of vehicles for sale in California in 1998 and ten percent of vehicles for sale in California in 2003 be zero emission vehicles, such as hydrogen fuel cell and battery electric vehicles. In 1996, due to pressure from auto companies and concerns about the state of technology, CARB eliminated the intermediate 1998 requirement, but kept the 2003 target of 10 percent zero-emission vehicles in place. CARB also allowed credits for partial zero emission vehicle (PZEV) credits for vehicles that were not 100 percent electric (e.g., hybrid electric vehicles). Soon afterwards, many of the auto companies introduced battery electric vehicles (BEV), including the GM EV1, Toyota EV RAV4, Ford Electric Ranger, and the Nissan Altra.
In 2001, CARB again changed the ZEV regulation to allow auto companies to meet the 10 percent requirement through three new vehicle categories:

Vehicle Category 

Percentage of Vehicles

Vehicle Type

Pure Zero Emission


Hydrogen Fuel Cell Vehicles
Battery Electric Vehicles

Advanced Technology Partial-ZEV (AT-PZEV)


Hybrid Electric Vehicles

Partial ZEV


Ultra-clean Gasoline Vehicles

The auto companies sued to block the changes, and in 2003, CARB developed the standards we see today: a complex system that allows the banking of credits. CARB also created the Alternative Path which requires significantly fewer hydrogen fuel cell vehicles to encourage their development.

Endings and Beginnings

Around the time of the lawsuits, most car companies ended their BEV programs citing limited demand and slow battery technology development. Proponents of these vehicles asserted that the demand existed despite the lack of support from the auto companies. This debate has not been resolved, but the cost and limited range of the BEV limits its use to certain applications and drivers. Still, the Toyota EV RAV4 is in use today by some utility companies and consumers. 

The end of battery electric vehicles era marked the beginning of a new age of hybrid and fuel cell vehicles, including the introduction of the Toyota Prius, Honda Civic, Ford Escape and other hybrids. It also spurred the expansion of fuel cell vehicle programs and hydrogen fueling stations across California.

The latest changes to the ZEV regulations in 2008 promoted the development of plug-in hybrids that use more electricity by recharging from the electrical grid.  CARB also agreed to overhaul the ZEV program beginning in 2015 to focus on California's long-term global warming goals.  UCS will be working to ensure that these sweeping changes will bring large numbers of electric, hybrid, and fuel cell vehicles to California. 

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