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Plug-in hybrid electric vehicles produce almost five times more global warming pollution than official data indicate, according to a recent report.

Widening Gap In Lab and Actual CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This differs significantly with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” said a lead researcher involved in the study. “This gap is growing and creates a serious issue. As a result, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric power relative to overall distance. They found that just a quarter of travel was done in electric mode, while lab assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution amounts were well above lab estimates. That occurred because EV motors were not strong sufficient to operate alone, leading to combustion motors burning gasoline for nearly one-third of the distance completed in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV emissions enabled several large automaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 extra annually in running costs than would be estimated under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy discussions as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from member states with large automotive manufacturing.

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

An independent energy economics specialist, who was not involved with the study, called the report a “highly valuable addition” after years in which parts of the automotive industry claimed there was too little information to accurately assess actual emissions.

“These findings demonstrate, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel cars,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering this evidence.”