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Plug-in hybrid cars emit nearly five times greater global warming pollution than official figures indicate, according to a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a advocacy group. This contrasts significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers examined information from in-vehicle energy use meters of 800,000 cars registered in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” stated a lead researcher participating in the report. “That discrepancy is growing and poses a significant problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode relative to overall mileage. The team determined that only a quarter of travel was done in electric mode, while lab assumptions suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than official projections. This occurred because EV motors were insufficiently powerful enough to function independently, resulting to engines using fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed several major carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 more annually in operating costs than is assumed under lab conditions.

“The strong claims that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a transport analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into policy discussions as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large car manufacturing.

Several high-level politicians have proposed PHEVs as a possible “compromise” solution to include in the legislation.

One external energy policy expert, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which parts of the car sector argued there was insufficient information to properly assess real-world emissions.

“These findings demonstrate, without question, that the difference in official and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional vehicles,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with extreme care and considering that data.”