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Plugging In

Can the grid handle the coming electric vehicle load?

Fortnightly Magazine - June 2010

vehicles, so they probably will be attractive to only a limited segment of drivers. These may be the same drivers that currently favor more fuel-efficient vehicles (including HEVs) and whose driving patterns reflect a high proportion of urban travel. While this factor might complicate the estimation of gasoline savings from PEV penetration ( i.e., because PEVs might tend to replace fuel-efficient conventional vehicles), it does suggest a distinct geographic pattern of initial PEV concentration—largely in urban areas on the East and West coasts. However, PEVs might be embraced for reasons beyond a strict cost advantage, and supportive public policies coupled with innovative designs and effective marketing could help to broaden their appeal.

DOE’s Energy Information Administration (EIA) has estimated that the annual sales of PEVs will grow to almost 140,000 vehicles by 2015, and 400,000 vehicles by 2030, supported by tax credits enacted in 2008—currently $2,500 per vehicle, plus $417 per kWh of battery capacity in excess of 5 kWh. An MIT report assumes plug-in hybrids will account for 2-3 percent of new vehicle sales by 2020, and 10 percent by 2030. 5 A much more optimistic scenario developed by the Electric Power Research Institute (EPRI) assumes 35 percent for 2020, and 50 percent for 2030. 6 Of course, for a new technology with adoption rates ramping up, its share of the overall vehicle fleet will be considerably lower than its share of new vehicle sales, because the fleet is only gradually replaced by new vehicles.

The National Research Council released a study that projected a “maximum practical” overall fleet penetration of PHEVs of about 13 percent by 2030, with a “more probable” penetration of less than 5 percent by that time. 7 The ISO/RTO Council’s March 2010 report estimates 1 million PEVs will be sold within five to 10 years, also concluding that early adoption would cluster in urban centers. The faster trajectory leads to a total of about 2.5 million vehicles by 2020—about 1 percent of the light duty vehicle fleet, though with a fair amount of geographic concentration that could mean a larger impact in some areas.

Overall, the market penetration of PEVs likely will be limited to a few percent of new vehicle sales over the next decade, and a smaller share of the vehicle fleet. If some of the barriers to PEV adoption can be overcome quickly, and consumer acceptance is high, it appears possible, albeit very optimistic, that PEVs might achieve as much as a 20-percent share of new vehicle sales and 5 percent of the vehicle fleet in some urban regions by 2020, potentially growing more quickly thereafter. But there are potential grid implications of this optimistic level of PEV penetration over the next decade.

Impact on the Grid

A study by Pacific Northwest National Laboratory showed that up to 84 percent of U.S. cars, pickup trucks, and SUVs theoretically could be converted to plug-in hybrids without requiring additional electric infrastructure ( i.e., by charging vehicles only at off-peak times to utilize electric generating capacity that’s otherwise idle). 8 However, it’s unlikely that