The cost for electricity to power plug-in hybrids for all-electric operation has been estimated at less than one quarter of the cost of gasoline in California.[1] Compared to conventional vehicles, PHEVs reduce air pollution locally and dependence on petroleum. PHEVs may reduce greenhouse gas emissions that contribute to global warming,[2][3] compared with conventional vehicles. PHEVs also eliminate the problem of range anxiety associated with all-electric vehicles, because the combustion engine works as a backup when the batteries are depleted, giving PHEVs driving range comparable to other vehicles with gasoline tanks.[4][5][6] Plug-in hybrids use no fossil fuel at the point of use during their all-electric range. Greenhouse gas emissions attributable to operation of plug-in hybrids during their all-electric range depend on the type of power plant that is used to meet additional demand[7] on the electrical grid at the time and place where the batteries are charged. (See Greenhouse gas emissions, below.) If the batteries are charged directly from renewable sources off the electrical grid, then the greenhouse gas emissions are essentially zero. Other benefits include improved national energy security, fewer fill-ups at the filling station, the convenience of home recharging, opportunities to provide emergency backup power in the home, and vehicle-to-grid (V2G) applications.[8][9] Several countries, including the United States and several European countries, have enacted laws to facilitate the introduction of PHEVs through grants and tax credits, emissions mandates, and by financing research and development of advanced batteries and other related technologies.