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Plug-in hybrid electric vehicles emit nearly five times more planet-heating pollution than lab-reported figures indicate, according to a new report.

Widening Gap In Lab and Actual CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional petrol and diesel cars, according to analysis carried out by a advocacy group. This contrasts significantly with laboratory tests, which assumed a 75% decrease in emissions.

Researchers examined information from onboard energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a lead analyst participating in the study. “This discrepancy is widening and poses a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to total mileage. They determined that just a quarter of driving was done in electric mode, while lab assumptions assumed over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to combustion motors using gasoline for nearly one-third of the distance completed in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 extra annually in running expenses than would be assumed under laboratory conditions.

“The bold claims that automakers like to make about their PHEV vehicles are obviously far from the mark,” stated a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been drawn again into policy debates as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large car manufacturing.

Several senior officials have suggested PHEVs as a potential “flexibility” option to introduce in the legislation.

One independent energy policy expert, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which parts of the automotive industry claimed there was insufficient information to accurately evaluate actual CO2 output.

“These findings demonstrate, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” they said. “Any policy changes regarding PHEVs should be implemented with utmost caution and considering that evidence.”