PZEVs come by way of California's Zero Emission Vehicle (ZEV) mandate, a vital portion of the state's low emission vehicle program dating back to 1990. Throughout history, CA has set a tight green benchmark for stringent emissions laws that have in turn led to tighter federal regulations. Vehicles are required to meet tight emission test requirements for volatile organic compounds (VOC), oxides of nitrogen (NOx), and carbon monoxide (CO). While it was thought that battery electric vehicles would be numerous on roads by now, problems from cost to range--and even marketing issues--led to a modification of the ZEV mandate that gave birth to the PZEV, the partial zero emissions vehicle which allows automakers to meet their quotas through partial zero credits.
The PZEV is not to be confused with the SULEV, the Super Ultra Low Emissions Vehicle, though. Yes, that's right. Another acronym to add to the bouillabaise. Buy a Prius in any other state than CA, and it'll be an SULEV. How come? Since most states don't offer California's cleaner low sulfur gas formulations, or the 150,000 mile emissions system warranty, cars that qualify as PZEVs in CA qualify as SULEVs in other parts of the country.