Plug in-hybrids falling short on fuel efficiency claims, says Which?

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everal popular plug-in hybrid cars (PHEVS) are 61% less fuel-efficient on average than manufacturers claim, a new study by Which? has revealed, hiking up consumer fuel costs by roughly £400 a year.

The independent lab fuel economy tests by the consumer choice firm revealed that the average fuel economy for the 22 models fell far below the official manufacturer claims, when accounting for 9,000 miles per year.

Based on the difference between manufacturer claims and the independent tests, the PHEVs with the greatest discrepancy were the BMW X5 Plug-in hybrid luxury SUV, the BMW 2 Series Active Tourer MPV and Mercedes Benz GLE Plug-in hybrid. In the face of concerns regarding range, inadequate charging infrastructure, and premium price tags, many carbon conscious individuals have opted for PHEVs as a stepping-stone in their transition to fully electric vehicle (EV).

Natalie Hitchins, head of home products and services at Which?, commented: “A fuel-efficient plug-in hybrid vehicle is an attractive feature for prospective buyers, as many will expect to spend less on fuel and reduce their carbon footprint.

“Yet our research shows many popular hybrid models are not as efficient as the manufacturer’s claim, which means motorists could be spending more on fuel than they anticipated.”

Fuel economy claims from manufacturers are based on the WLTP test cycle, which has been the official standard since 2017, when it replaced the NEDC test cycle as a more realistic representation of driving conditions. According to Which?, the independent tests which revealed the disparity are more stringent and tougher than those provided in the WLTP, more accurately reflecting the strain put on cars in real life.

Responding to the findings, Mercedes Benz argued: “We cannot comment on your results without understanding the methodology of your test – given the many factors and scenarios that can affect mpg. Official WLTP testing is performed in repeatable conditions and certified by government agencies – so Mercedes-Benz customers can be assured they provide accurate and comparable results.”