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Plug-in hybrid electric vehicles release nearly five times greater global warming pollution than official figures indicate, according to a recent report.

Growing Gap Between Official and Real-World CO2 Output

Statistics shows that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, according to research conducted by a advocacy group. This contrasts sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers examined information from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are falling,” stated a senior analyst participating in the report. “This discrepancy is widening and creates a serious problem. As a result, PHEVs pollute nearly as much as petrol cars.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total mileage. The team found that only 27% of travel was completed in EV mode, while lab assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above official estimates. This happened because electric motors were not strong enough to operate alone, resulting to combustion motors burning fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled several large automaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 more annually in running expenses than would be estimated under lab tests.

“The bold statements that manufacturers often promote about their PHEV cars are clearly way off the mark,” stated a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into policy discussions as carmakers have pressed the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large automotive industries.

Some high-level officials have suggested plug-in hybrids as a possible “compromise” option to include in the regulation.

An independent energy economics expert, who was unaffiliated with the research, described the report a “very useful addition” after a long period in which segments of the car industry argued there was insufficient information to properly assess actual emissions.

“These findings show, without question, that the gap between lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “All policy changes regarding PHEVs should be implemented with utmost caution and in the light of that evidence.”