The deployment of electric vehicles and plug-in hybrid vehicles on the premise of using low-carbon power sources (renewable energy and nuclear power) is expected to not only contribute to a stable energy supply by lowering dependence on oil (dependence on foreign supply sources) as fuel but also help to reduce CO2 emissions. Moreover, the use of night-time electricity is likely to help spread the use of electric vehicles for commuter use by reducing energy cost. However, it is important to remember that if conventional electricity, mainly generated by coal-fired power plants, is to be used as a power source, the deployment of electric vehicles and plug-in hybrid vehicles may not necessarily be effective in reducing CO2 emissions.
It is also true that compared with vehicles powered by an internal-combustion engine, electric vehicles still have some shortcomings, such as their short driving range, some 100 km on a single charge of the battery, and the long battery-recharging time. To significantly increase the use of electric vehicles in the future, the key will be to develop a low-cost, high-performance battery. It will also be necessary to further reduce the cost of wind and photovoltaic power generation.
As the use of electric vehicles spreads, it will become necessary to conduct a quantitative study on the optimization (cost minimization) of the power source mix (cost minimization), including additional power sources for automobiles.