Plug-in hybrid electric vehicles--touted as a storage medium for renewable energy that can help regulate the grid and a key to reducing air pollution, greenhouse gases, and dependence on foreign oil--are eight years away from mass commercialization, the California Air Resources Board heard at its May 24-25 meeting. However, California motorists may begin seeing significant numbers of plug-in hybrid vehicles before then, according to an expert panel report to the air board on the state of zero-emissions-vehicle technology. The panel forecast that automakers are likely to begin producing precommercial volumes of plug-in hybrid electric vehicles around 2010--numbering in the thousands a year. Commercial volumes reaching tens of thousands of new plug-ins a year are expected as early as 2012. Production then is expected to quickly ramp up to a mass-production volume of 100,000 or more a year by 2015. Meanwhile, full-powered battery electric vehicles are unlikely to see mass commercialization until 2030. Plug-in hybrids, however, are considered environmentally beneficial because much of the time they function just like a full-powered battery electric vehicle. Drivers can charge them up off the grid with relatively clean energy, or even emissions-free renewable energy. Motorists then can drive the vehicles to and from work on average-length commutes without using their onboard gasoline engines. Those are reserved for longer trips. According to the report to the air board, Status and Prospects for Zero Emissions Vehicle Technology, the first plug-in hybrids are likely to use existing hybrid vehicle platforms but will be beefed up to provide higher energy-storage levels over the years as battery costs decline.