Wired magazine reports that the city of Seattle recently received a surprising lesson in hybrid economics. After it converted a dozen of its Toyota Prius hybrid fleet cars to plug-in hybrids, Seattle administrators said they never achieved the 100-mpg fuel efficiency they had expected.
In fact, the vehicles averaged “only” about 51 mpg, raising concerns that future plug-in hybrids “may not catch on if consumers don’t see the fuel efficiency they’re promised.”
For me, though, this raises a different question: Should we be measuring plug-in hybrids in terms of how much gasoline they burn? For the last couple of years, makers of plug-ins have been bandying miles-per-gallon numbers around without regard to the meaningfulness of those numbers. In 2007, GM’s Bob Lutz declared that the Chevy Volt could nearly eliminate trips to the gas station. “If you lived 30 miles from work and charged your vehicle every night when you came home or during the day at work, you could get 150 miles per gallon,” he said.
Well, yes, if you run a car on batteries alone, you wouldn’t expect it to burn much gasoline, would you? But, at some point, you’ve got to wonder how valuable it is to tell consumers that they’re getting great gas mileage when they run on electricity.
To be sure, the Prius’ parallel hybrid configuration differs from that of the Chevy Volt, and the operational modes are vastly different. But the problems are still the same: Plug-in hybrid energy consumption depends on how the vehicles are used, how hard the drivers step on their accelerators, how far they drive, and how often they recharge. So by predicting mileage numbers of 100 mpg or 150 mpg, auto makers are just going to confuse consumers with inaccurate, meaningless figures.
If the auto industry is concerned about alienating hybrid owners, maybe it should search for a better way to express plug-in hybrid energy consumption. Otherwise, there’s going to be a lot of confused car buyers out there.