2. 插电式混动

    插电式混动车也叫PHEV，它与油电混动车类似，但电池容量更大，能光靠电能推动车行驶一定距离，也因此实现了零排放。这种电池随后能插在电源上充电。容量更大的电池成本也随之水涨船高——比如插电式普锐斯在最近降价前就需要多花7,000美元——而且目前美国在售的PHEV只有四种。通用汽车（General Motors）那款大名鼎鼎的增程式雪佛兰沃蓝达（Volt）每月销量也不足2,000辆。

    2. Plug-in hybrids

    Plug-in hybrids or PHEVS are similar to gas-electric hybrids but have larger batteries that can propel the car limited distances on electricity alone, thus generating zero emissions. The batteries can then be recharged by being plugged into an electric power source. The cost of the larger batteries carries a hefty price premium -- an additional $7,000 for the plug-in version of the Prius before a recent price cut -- and only four PHEV models are currently available in the U.S. Sales of the best-known model, General Motors' (GM,Fortune 500) range-assisted Chevrolet Volt (above), have been running at less than 2,000 a month.