 Cumulative plug-in electric car sales since 2008 reached the 250,000 units in August 2014, 500,000 in August 2016, and the one million goal was achieved in September 2018.According to the U.S. Department of Energy, combined sales of plug-in hybrids and battery electric cars are climbing more rapidly and outselling by more than double sales of hybrid-electric vehicles over their respective 24 month introductory periods, as shown in the graph at the right.A more detailed analysis by the Office of Energy Efficiency and Renewable Energy over the same two-year introductory periods found that except for the initial months in the market, monthly sales of the Volt and the Leaf have been higher than the Prius HEV, and the Prius PHEV has outsold the regular Prius during its 8 months in the market.