Data gathered by the International Council on Clean Transportation (ICCT) suggests that the drivers of plug-in hybrid vehicles use their electric powertrain far less than previously assumed. That means that the vehicles are using more gas for their internal combustion engine than regulators at the Environmental Protection Agency (EPA) estimate in their labeling program.
The study found that, in the real world, the share of driving handled entirely by electric motors is 26 to 56 percent lower than the EPA assumes when it is labeling the fuel efficiency of the vehicles. As a result, the real world fuel consumption tends to be 42 to 67 percent higher than the regulator estimates.
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