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PHEVs produce nearly five times more global warming pollution than lab-reported data show, according to a recent analysis.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy group. This contrasts significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers studied data from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a senior analyst involved in the study. “This gap is growing and creates a significant problem. As a result, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of miles driven in battery power relative to total mileage. The team found that only 27% of travel was done in electric mode, whereas official estimates suggested 84%.

Additionally, when operating in electric mode, emission amounts were well above official projections. That happened because electric motors were insufficiently powerful sufficient to operate alone, leading to engines burning fossil fuels for almost one-third of the travel covered in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several major automaker groups to escape over €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in operating expenses than is estimated under laboratory conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been drawn back into political discussions as automakers have lobbied the European Union to relax CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from member states with large automotive manufacturing.

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

An independent energy economics expert, who was not involved with the study, called the report a “highly valuable addition” after a long period in which parts of the car industry claimed there was insufficient information to properly evaluate real-world CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” they stated. “All regulatory changes concerning PHEVs should be made with extreme care and in the light of that data.”