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Plug-in hybrid electric vehicles produce nearly 5x more global warming pollution than official data indicate, according to a recent report.

Growing Gap Between Lab and Actual Emissions

Data shows that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit organization. This differs sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” stated a lead researcher participating in the report. “That gap is growing and poses a serious problem. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to overall mileage. The team found that just a quarter of travel was done in electric mode, whereas official estimates assumed over four-fifths.

Additionally, when running in electric mode, emission levels were well above official estimates. That occurred because electric motors were not strong enough to function independently, resulting to engines burning fossil fuels for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four major carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 extra per year in running expenses than would be estimated under lab conditions.

“The bold statements that manufacturers like to make about their PHEV vehicles are clearly way off the mark,” stated a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Hybrid cars have lately been drawn back into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from member states with significant car manufacturing.

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

One independent energy economics expert, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which parts of the car industry argued there was too little data to accurately assess real-world CO2 output.

“These findings show, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” the expert said. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering this evidence.”