Climate Change Policy Partnership

Plug-In Hybrids No Better Than Regular Hybrids for Reducing Carbon Dioxide Emissions Today

Contact: Eric Roston, 202/ 797-6500, Eric.Roston@duke.edu, or Eric Williams, 919/ 613-8714, e.l.williams@duke.edu

December 9, 2008

DURHAM, N.C. – Both plug-in hybrid electric and regular hybrid vehicles have the potential to reduce carbon dioxide emissions associated with global warming and revitalize sales for Detroit’s Big Three carmakers – a fact driven home, symbolically, when the CEOs of General Motors, Ford and Chrysler drove hybrids to Capitol Hill on Dec. 4 to present their bailout proposal to Congress.

Yet a new working paper by Duke University researchers finds that regular hybrids lower carbon dioxide emissions as effectively as plug-in hybrids, but at a considerably lower cost, despite recent focus on plug-ins by policymakers.

In the paper, online at www.nicholas.duke.edu/ccpp/publications.html, Eric Williams, co-director of Duke’s Climate Change Policy Partnership (CCPP), compares the two hybrid technologies to see which could lead to lower carbon dioxide emissions, operating costs and overall consumer costs under a variety of scenarios. He finds that:

Without a CO2 price signal, plug-in hybrids are essentially no better than regular hybrids at reducing CO2 emissions;

With a significant CO2 price signal, plug-ins reduce moderately more CO2 emissions than regular hybrids;

Plug-in hybrids are significantly more expensive than hybrids at current gas prices; plug-ins become cost-effective at $6 a gallon;

Certain regions are poorly suited for plug-ins because they have carbon-intensive electricity systems; for plug-ins to reduce carbon dioxide emissions as effectively as hybrids in these regions, a carbon price is necessary and the deployment of carbon capture and storage technology may also be critical.

“It’s not a simple equation,” Williams explains. “Plug-in hybrids save gasoline but consume electricity. In most of the country, electricity generation relies on fossil fuels, which means that plug-ins would lead to an increase in electricity sector fossil fuel consumption and CO2 emissions. At the same time, plug-ins would reduce direct vehicle emissions. Taking this into account, I wanted to see how net emissions change, regionally and nationally, as a result of plug-ins.”

The answer to that question, he notes, depends largely on whether there is a price signal for CO2 emissions. If federal or regional climate legislation places a limit on the amount of CO2 allowed, it will create a price signal that will drive the electricity sector to become more efficient and less carbon intensive. In this case, Williams says, plug-in hybrids would typically enjoy lower CO2 emissions nationally and in most regions compared to regular hybrids.

“However, in a few carbon-intensive regions where electricity generation relies heavily on coal, plug-in hybrids would have lower net emissions than conventional vehicles, but not lower than regular hybrids,” he says. “With respect to carbon mitigation, policymakers may want to focus on regular hybrids for certain regions rather than plug-in hybrids, even with a CO2 price signal.”

In the absence of a price signal for CO2 emissions, Williams’ analysis gives the edge to regular hybrids. Nationally, plug-ins and regular hybrids reduce C02 emissions by about the same amount without a CO2 price signal, he finds, but regular hybrids can do it at considerably lower cost.

CCPP is an interdisciplinary research partnership of Duke’s Nicholas Institute for Environmental Policy Solutions, Nicholas School of the Environment and Center on Global Change. CCPP researches carbon-mitigating technology, infrastructure, institutions and systems to inform lawmakers and business leaders as they lay the foundation of a low-carbon economy.