Recommendation 4-7. U.S. DRIVE should include the CNG vehicle and possible improvements to its analysis efforts in order to make consistent comparisons across different pathways and to help determine whether CNG vehicles should be part of its ongoing vehicle program.


The amount of electricity required for individual plug-in vehicle16 travel depends on vehicle size, weight, and other characteristics. The Environmental Protection Agency (EPA) estimates that the midsize Nissan Leaf uses an average of 34 kWh per 100 miles and that the Transit Connect Van uses 54 kWh per 100 miles.17 Most forecasts of plug-in vehicle demand suggest that the national electric-supply-system grid will be able to support the number of electric vehicles likely to be on the road, at least to 2020. Some local supply problems could appear, possibly in Texas, for example, where a combination of grid isolation and weak incentives for new generation appear likely to cause shortages. And in some neighborhoods the clustering of plug-in vehicles might overload local circuits and transformers. But from a national perspective, the near-term grid capacity appears adequate.

Beyond that time, the energy capacity projected for the U.S. electric system also appears ample as long as the projected capacity additions are brought online (see Box 4-1). Nevertheless, three kinds of uncertainty—demand uncertainty, technology uncertainty, and policy uncertainty—will require leadership from DOE and the U.S. DRIVE Partnership to ensure the most rapid, environmentally benign market penetration and cost-effective penetration of plug-in vehicles.

Three Consequential Uncertainties

Even though the national grid appears adequate, the three uncertainties listed above remain. Their resolution will strongly influence the environmental and economic consequences of recharging plug-in vehicles as well as the pace of the acceptance of plug-in vehicles in the marketplace. Resolving the uncertainties in a favorable manner will require rapid learning and effective response on the part of DOE, the U.S. DRIVE Partnership, and state policy makers. Discussed in the sections below, the uncertainties can be briefly described as follows:

  • Demand uncertainty regarding the ways that consumers will recharge these vehicles, and how (or whether) customers will use “smart-home”


16 “Plug-in vehicle” here is meant to include any vehicle relying on electric energy that is supplied externally, most likely from the national electric grid. In the terms most commonly used, this includes battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and extended-range electric vehicles (EREVs). Generically, since all of these vehicles are dependent to one extent or another on electricity from the grid, they are sometimes all referred to as electric vehicles (EVs).

17 See, for example,

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