Plug-in Hybrid electric Cars Emit Almost as Much as Gasoline Vehicles, Study Finds

Plug-in hybrid cars release nearly five times greater planet-heating emissions than lab-reported figures indicate, according to a new analysis.

Widening Discrepancy In Official and Real-World Emissions

Data reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That contrasts significantly with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a lead researcher participating in the study. “This gap is growing and poses a serious issue. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode compared to total mileage. The team determined that just a quarter of travel was completed in electric mode, while lab assumptions suggested 84%.

Even, when running in EV mode, emission levels were well above lab projections. That occurred because electric motors were not strong sufficient to function alone, leading to combustion motors burning gasoline for almost a third of the distance completed in EV mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions allowed four large automaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs would spend about €500 more annually in running expenses than is estimated under lab conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the mark,” stated a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with significant car industries.

Some senior officials have suggested plug-in hybrids as a potential “compromise” option to include in the regulation.

One external energy economics expert, who was unaffiliated with the study, called the report a “very useful contribution” after a long period in which parts of the automotive sector argued there was insufficient data to properly assess real-world emissions.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert stated. “Any policy adjustments regarding PHEVs should be made with utmost caution and considering that data.”