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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating pollution than official data indicate, as per a new analysis.

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy group. This differs significantly with lab tests, which suggested a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of 800,000 cars sold in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” stated a lead researcher involved in the study. “This discrepancy is widening and poses a serious issue. As a result, PHEVs pollute nearly as much as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to total distance. The team found that only 27% of driving was completed in EV mode, while official estimates suggested over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than official estimates. This happened because electric motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed four major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

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

“The strong claims that automakers often promote about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought back into political discussions as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from member states with large car manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “compromise” option to include in the legislation.

One independent energy economics specialist, who was not involved with the research, described the report a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little information to properly evaluate actual CO2 output.

“These findings demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering that data.”