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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating pollution than official figures show, according to a recent report.

Widening Gap In Lab and Real-World CO2 Output

Data shows that PHEVs emit only 19% less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy group. This contrasts significantly with lab estimates, which assumed a 75% reduction in pollution.

Analysts examined information from onboard fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior researcher participating in the study. “That gap is growing and poses a serious problem. Consequently, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Behind the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to overall distance. The team determined that only a quarter of travel was completed in electric mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than lab estimates. That happened because electric motors were not strong sufficient to function alone, leading to combustion motors using gasoline for nearly a third of the travel covered in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output enabled four large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would pay about €500 extra per year in running expenses than is estimated under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are obviously way off the truth,” stated a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into policy discussions as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from member states with significant car industries.

Several senior politicians have suggested PHEVs as a potential “compromise” solution to include in the regulation.

An independent energy economics expert, who was not involved with the study, described the report a “very useful addition” after a long period in which parts of the automotive sector claimed there was too little data to accurately assess actual CO2 output.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ output is significantly larger than for petrol or diesel vehicles,” they said. “Any policy adjustments concerning PHEVs should be made with utmost care and in the light of this evidence.”