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Plug-in hybrid cars emit nearly five times greater global warming pollution than lab-reported data indicate, as per a recent analysis.

Widening Gap In Official and Actual Emissions

Statistics shows that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit organization. That differs sharply with laboratory tests, which suggested a three-quarters decrease in emissions.

Analysts studied data from in-vehicle energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a lead researcher participating in the report. “This gap is widening and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to total mileage. They found that only a quarter of travel was done in electric mode, whereas lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab estimates. This happened because EV motors were not strong enough to operate independently, resulting to combustion motors burning gasoline for almost a third of the travel covered in electric mode.

Regulatory and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled several large automaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 more per year in operating expenses than would be estimated under lab tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant automotive industries.

Some senior officials have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the study, called the report a “highly valuable addition” after years in which parts of the automotive sector argued there was too little information to properly evaluate real-world CO2 output.

“The results show, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” they said. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and in the light of that evidence.”