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Plug-in hybrid cars emit almost five times more planet-heating pollution than lab-reported figures indicate, according to a recent report.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit group. This differs sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 cars registered in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” stated a lead researcher involved in the report. “This discrepancy is widening and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles driven in battery power compared to total mileage. The team determined that just 27% of travel was completed in EV mode, whereas lab estimates suggested over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors burning gasoline for almost one-third of the travel completed in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

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

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” stated a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn again into policy discussions as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car manufacturing.

Several senior officials have proposed plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

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

“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 diesel vehicles,” the expert said. “Any policy changes concerning PHEVs should be made with utmost care and in the light of this data.”