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PHEVs emit almost five times greater planet-heating pollution than official figures indicate, according to a recent report.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit organization. This contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Analysts examined data from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a senior analyst participating in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in battery mode relative to overall mileage. The team found that only a quarter of travel was completed in EV mode, whereas official estimates assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were well above official estimates. This happened because EV motors were not strong enough to function independently, leading to combustion motors using fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed four large automaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

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

“The strong claims that automakers like to make about their plug-in hybrid cars are obviously far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into policy debates as automakers have pressed the EU to relax CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large automotive manufacturing.

Some high-level politicians have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

One independent energy policy specialist, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which segments of the car industry argued there was too little data to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional cars,” they said. “All policy changes regarding PHEVs should be made with utmost care and in the light of this data.”