Plug-In Hybrids Can Be Worse Than Gas Cars: GM Executive Shares an Uncomfortable Truth

General Motors CEO Mary Barra has criticized plug-in hybrid (PHEV) owners for overusing their internal combustion engines, pointing to real-world usage data and its environmental consequences.

Speaking recently at the Automotive Press Association conference in Detroit, Barra said that a large share of PHEV owners rarely — or never — plug their vehicles in. As a result, the expected environmental benefits of electrified vehicles are effectively erased, while real-world emissions increase. Fast Company first reported the comments.

According to Barra, early assumptions suggested that roughly 84% of all trips in plug-in hybrids would be driven purely on electric power. However, recent studies show the actual figure is nowhere near that level — just 27%. In practice, many PHEV drivers simply rely on the gasoline engine that’s always available, rather than taking the extra step of charging the battery from the grid.

As a consequence, real-world emissions can be significantly higher than the official figures listed for plug-in hybrids, which are calculated under the assumption that the battery is used to its fullest extent. Once the battery is depleted, the relatively small internal combustion engines in PHEVs are forced to operate under higher loads. Combined with the added weight of the battery system, this means that in certain conditions a conventional gasoline-powered vehicle can actually be more efficient — and greener — than a plug-in hybrid.