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PHEVs release nearly five times more global warming emissions than lab-reported data show, according to a new analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, according to research carried out by a non-profit organization. That contrasts significantly with lab tests, which suggested a 75% reduction in pollution.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 cars registered in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a lead researcher involved in the study. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to total distance. The team found that just 27% of travel was done in EV mode, whereas lab estimates assumed 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab projections. This happened because EV motors were insufficiently powerful enough to function alone, leading to combustion motors using gasoline for nearly one-third of the travel completed in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV emissions allowed four major carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would pay about €500 extra annually in operating costs than is estimated under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been drawn again into political debates as automakers have lobbied the European Union to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant automotive industries.

Some high-level politicians have proposed PHEVs as a potential “compromise” solution to include in the legislation.

One independent energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector argued there was insufficient data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they stated. “Any policy changes regarding PHEVs should be made with extreme care and in the light of this data.”