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PHEVs emit nearly 5x more planet-heating pollution than official data indicate, according to a recent report.

Widening Gap Between Official and Actual Emissions

Data reveals that PHEVs emit only 19% less CO₂ than traditional petrol and diesel cars, according to analysis conducted by a advocacy organization. That differs significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a lead researcher participating in the study. “This gap is widening and creates a serious problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery power relative to total mileage. They determined that just 27% of driving was done in electric mode, whereas lab assumptions suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab projections. This happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors burning fossil fuels for almost one-third of the distance covered in electric mode.

Regulatory and Financial Implications

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

Additionally, owners of PHEVs could pay approximately €500 extra annually in running expenses than is assumed under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant car manufacturing.

Some high-level politicians have proposed PHEVs as a possible “compromise” option to include in the regulation.

One independent energy policy expert, who was not involved with the study, described the analysis a “very useful addition” after years in which segments of the automotive sector argued there was too little data to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with utmost care and in the light of this evidence.”