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Plug-in hybrid cars release nearly 5x greater global warming pollution than official data show, as per a recent analysis.

Growing Gap Between Official and Real-World Emissions

Data reveals that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, according to analysis carried out by a non-profit group. That differs significantly with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a senior researcher participating in the study. “This discrepancy is widening and poses a serious issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric power compared to overall distance. They found that only a quarter of travel was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Even, when running in electric mode, pollution levels were well above lab estimates. This occurred because EV motors were insufficiently powerful enough to function independently, leading to engines burning gasoline for nearly a third of the distance covered in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend approximately €500 more annually in running expenses than is assumed under laboratory tests.

“The strong claims that manufacturers like to make about their PHEV cars are obviously far from the truth,” commented a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn again into political debates as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large automotive manufacturing.

Several high-level politicians have proposed PHEVs as a potential “flexibility” option to introduce in the regulation.

An external energy policy specialist, who was unaffiliated with the study, described the report a “highly valuable addition” after a long period in which parts of the car industry claimed there was insufficient data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of that data.”