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PHEVs emit nearly 5x more planet-heating pollution than official figures indicate, according to a recent report.

Widening Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a advocacy group. This contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers studied data from onboard energy use meters of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” said a lead researcher involved in the study. “That discrepancy is growing and creates a significant problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode relative to total mileage. They determined that only a quarter of travel was done in electric mode, whereas lab estimates suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab projections. This occurred because EV motors were insufficiently powerful sufficient to operate independently, leading to combustion motors using fossil fuels for almost a third of the distance covered in electric mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed four large carmaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra annually in running expenses than would be assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their PHEV cars are obviously way off the mark,” stated a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid cars have recently been brought again into political discussions as carmakers have pressed the EU to relax CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from member states with large car industries.

Some high-level politicians have suggested plug-in hybrids as a potential “compromise” solution to include in the legislation.

An independent energy policy expert, who was not involved with the research, called the analysis a “highly valuable contribution” after years in which segments of the car sector claimed there was insufficient data to properly assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” the expert said. “Any policy changes concerning PHEVs should be made with extreme caution and considering that data.”