 General Motors launched the 2011 Chevrolet Volt series plug-in in December 2010.At the time, the Volt displaced the Toyota Prius as the most fuel-efficient car sold in the United States., the Volt/Ampera family is the world's all-time best-selling plug-in hybrid car, with global sales totaling about 134,500 units since its inception, including over 10,000 Opel/Vauxhall Amperas sold in Europe.