BOX 4-1
The Plug-in Vehicle and the U.S. Electric Supply System

The impact of the plug-in vehicle on the grid depends on the market penetration of electric vehicles (EVs, which include both plug-in electric vehicles [PHEVs] and battery electric vehicles [BEVs]). Forecasts vary widely. For example, Deloitte Consulting projects the 2020 U.S. market share for EVs to range from 2.0 to 5.6 percent of the new-vehicle market, or between 285,000 and 840,000 vehicles per year (LaMonica, 2010). Also, projects annual EV sales of 250,000 by 2017, which would put it within the Deloitte range by 2020 (Shepardson, 2012).

If it is assumed conservatively that the number of PHEVs sold increases linearly to reach 1 million per year by 2020, that would imply an EV fleet of, at most, 4 million vehicles operating in that year. If each of these vehicles recharges a 10-kWh (usable depth-of-discharge) battery twice a day, every day for a year, the total kilowatt-hours consumed in 2020 would be about 29 billion. In contrast, the Energy Information Administration estimates that the national electric grid will be able to produce 4,159 billion kWh in 2020 (EIA, 2012). Thus even a highly optimistic case for plug-in vehicle penetration suggests that the electric energy demand of plug-in vehicles will prove manageable.

To be sure, a national or even state restriction on carbon emissions severe enough to shut down large numbers of coal-fired power plants could make this forecast unachievable. But absent such an occurrence and from a national perspective, the energy demands imposed by the EV fleet appear to be manageable.

  • technologies in ways that offset the grid impacts of plug-in vehicle charging;
  • Technology uncertainty regarding the speed of deployment of smart-grid technologies and advanced charging systems that allow rapid charging; and
  • Policy uncertainty regarding the nature and strength of rate incentives for consumers to recharge their vehicles and for the electric utility companies or others to invest in the necessary infrastructure.

These uncertainties cannot be addressed independent of one another, but rather must be resolved in their entirety. Leadership from DOE and the U.S. DRIVE Partnership will prove essential for their timely and effective resolution. Absent that leadership, the market penetration of all plug-in vehicles could be delayed and their environmental and economic benefits blunted.

Demand Uncertainty

The location and time at which the users of plug-in vehicles will choose to recharge their batteries remain quite uncertain for several reasons. First, regarding location, many grid analysts note the tendency of plug-in ownership to occur in

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