Emissions from Hybrid and Plug-In Electric Vehicles  Hybrid
electric vehicles (HEVs), plug-in hybrid electric vehicles
(PHEVs), and all-electric vehicles (EVs) typically produce lower
emissions than conventional vehicles do. When measuring well-to-
wheel emissions, the electricity source is important: For PHEVs
and EVs, part or all of the power comes from off-board sources
of electricity. There are emissions associated with the majority
of electricity production in the United States.  Electricity
Sources and Emissions  EVs and PHEVs running only on electricity
have zero tailpipe emissions, but emissions may be produced by
the source of electrical power, such as a power plant. In
geographic areas that use relatively low-polluting energy
sources for electricity generation, PHEVs and EVs typically have
a well-to-wheel emissions advantage over similar conventional
vehicles running on gasoline or diesel. In regions that depend
heavily on conventional fossil fuels for electricity generation,
PEVs may not demonstrate