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Plug-in hybrid cars release almost five times greater planet-heating pollution than official figures show, as per a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Data reveals that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. That differs sharply with laboratory tests, which assumed a 75% decrease in pollution.

Analysts examined data from onboard fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” stated a senior analyst participating in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery power relative to overall mileage. They determined that just 27% of travel was completed in EV mode, whereas official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab projections. That occurred because EV motors were not strong enough to function independently, resulting to combustion motors burning gasoline for almost one-third of the distance covered in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled several large carmaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 more per year in operating costs than is estimated under laboratory tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little better than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant automotive industries.

Several high-level officials have suggested PHEVs as a possible “compromise” option to include in the regulation.

One external energy policy expert, who was not involved with the research, called the report a “very useful contribution” after a long period in which segments of the car sector argued there was insufficient data to accurately assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” the expert said. “Any policy changes regarding PHEVs should be implemented with utmost caution and considering that evidence.”