Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
based on the type of electricity grid generation used to charge them, but scenarios
assuming a move to increasingly cleaner electricity generation sources suggest a potential
for up to a 68 to 80 percent GHG reduction per vehicle in 2030, or 78 to 87 percent in 2050.
Although market penetration estimates also are highly uncertain for BEVs, illustrative
market penetration scenarios would result in anywhere from 47 to 55 mmt CO 2e annually
in the medium term (2.2 to 2.5 percent of transportation emissions in 2030), and between
570 and 640 mmt CO 2e annually in the long term (26 to 30 percent of emissions in 2050),
assuming favorable consumer acceptance. These estimates assume a maximum BEV
market penetration of approximately 5 percent of the light-duty vehicle stock in 2030 and
56 percent in 2050, with the emissions range reflecting the uncertainty associated with the
source mix used for battery charging.
Advancements in battery technology, especially with regards to cost, could make BEVs
viable in the medium to long term, and a shift in grid generation to a greater proportion of
renewable sources could allow BEVs to significantly reduce GHG emissions from the
transportation sector. Plug-in hybrid electric vehicle (PHEV) technology (see Section 3.2.4)
may serve as a step on the path to significant BEV market share in the long term,
facilitating battery and other vehicle developments for enhanced BEV performance.
Consumer response will likely decisively impact the future of BEVs, with limited
operation range (less than 200 miles between charges) providing a significant constraint on
acceptability. While even in the long-term BEVs are estimated to be substantially more
expensive than conventional vehicles (between $6,000 and $10,000 depending upon the
range of the vehicle), low nighttime charge rates would result in operation costs per mile
that are about 75 percent lower than for a gasoline vehicle, potentially yielding a net
savings over the life of the vehicle.
The Rebound Effect
Benefits from technology strategies may be somewhat offset due to the “rebound effect.”
This effect can be characterized as the extent to which any fuel cost savings (and
corresponding GHG reductions) from alternative fuels are offset by increased travel,
because travel is made cheaper per-mile due to reduced fuel costs. (Conversely, a fuel that
is more expensive per-mile could have the effect of reducing VMT and therefore providing
further GHG benefits.) The National Highway and Traffic Safety Administration
(NHTSA), used a 10 percent rebound effect in its analysis of fuel savings and other benefits
from higher CAFE standards for MY 2012-2016 vehicles. Recognizing the uncertainty
surrounding the 10 percent estimate, the agency analyzed the sensitivity of its benefits
estimates to a range of values for the rebound effect from 5 percent to 15 percent (NHTSA,
2009). (For more detail on the rebound effect, see Appendix A.)
The impact of the rebound effect is fairly straightforward to demonstrate in the case of
strategies that improve the efficiency of existing gasoline or diesel vehicles, as
demonstrated in Section 3.0. For alternative fuel strategies, it is more complicated to
estimate as the effects will depend upon the relative cost per mile of the different fuels
compared to gasoline. Some of the fuel strategies evaluated in this report will increase the
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