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Plug-in hybrid cars release nearly five times more planet-heating pollution than official data indicate, according to a new report.

Growing Gap Between Official and Actual CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy organization. This contrasts significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” stated a lead analyst participating in the study. “This discrepancy is growing and poses a serious issue. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the difference to overestimates of the “utility factor” – the percentage of miles travelled in battery power relative to total distance. The team found that just a quarter of travel was done in EV mode, whereas official estimates assumed 84%.

Additionally, when running in electric mode, pollution levels were well above lab estimates. That occurred because electric motors were not strong enough to operate independently, leading to engines burning gasoline for nearly one-third of the distance covered in EV mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed four major carmaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra annually in operating costs than is assumed under lab tests.

“The bold statements that automakers often promote about their PHEV cars are obviously way off the mark,” stated a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car industry and opposition from EU countries with significant automotive manufacturing.

Several high-level officials have suggested plug-in hybrids as a possible “flexibility” solution to include in the legislation.

An external energy policy specialist, who was not involved with the research, described the report a “very useful contribution” after years in which segments of the automotive industry argued there was insufficient data to accurately evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they said. “All regulatory changes concerning PHEVs should be implemented with utmost care and in the light of this data.”