在当今时代，大约有36种不同尺寸的混合动力车和23种插电式电动车。其中包括宝马i3豪华SUV，福特C-Max中型能源，以及两名乘客的Smart ED。随着汽油价格的不断上涨和电动汽车的销售价格的不断下降。电动汽车的普及率越来越高，当代美国的混合动力汽车近330万辆，插电式电动汽车23.4万辆(Sierzchula et al.， 2012a)。
电动汽车似乎不同于化石燃料汽车，电能的消耗可以通过多种来源产生，包括可再生能源、核能和化石燃料(Bakker et al.， 2012)。排放电动汽车的碳和其他来源的碳足迹涉及高度依赖发电技术和燃料的各种变化。然后可以使用超级电容器、飞轮或电池在车辆板上储存电能。涉及使用发动机的车辆，其工作原理基本上是燃烧，显然考虑从一些或单一来源的能源(Dijk et al.， 2013)。大多数时候，这些能源主要包括不可再生的化石燃料。插入式或混合动力汽车的一个主要好处是再生制动的属性，因为它们能够回收通常在制动过程中丢失的能量，因为电池中储存了电能。
In the current era, there are approximately 36 hybrid models and 23 plug-in electric models in a number of different sizes. Some of these are BMW i3 luxury SUV, Ford C-Max Energy of mid- size, and Smart ED for two passengers. As the prices of gasoline have been continuously rising and the prices at which electric vehicles are sold have been continuously dropping. There has been increased popularity of electric vehicles, with almost 3.3 million hybrids and 234,000 plug-in electric vehicles on the roads of United States in the current era (Sierzchula et al., 2012a).
Electric vehicles appear to be different from vehicles powered by fossil fuel in that the consumption of electricity can be generated out of a number of sources including renewable sources, nuclear power and fossil fuels (Bakker et al., 2012). The footprint of carbon and other sources emitting electric vehicles involve variations that are highly dependent upon the technology and fuel used for the generation of electricity. There may then be storage of electricity over board of the vehicle by the use of super- capacitors, flywheel or battery. Vehicles involving the utilization of engines that work as per the principle of combustion mostly and evidently consider deriving their energy out of some or a single source (Dijk et al., 2013). Most of the time, these sources are inclusive of non- renewable fossil fuels mostly. A major benefit of plug- in or hybrid electric vehicles is the attribute of regenerative braking because of their ability for recovering energy that is lost normally in the duration of braking as there is storage of electricity in the battery on- board.