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Plug-in hybrid cars produce nearly 5x more planet-heating emissions than official figures show, according to a new report.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a non-profit organization. That differs significantly with lab estimates, which assumed a 75% decrease in emissions.

Researchers studied data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a lead analyst involved in the study. “This gap is growing and creates a significant problem. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric mode compared to overall distance. They found that only a quarter of driving was completed in EV mode, whereas official assumptions assumed 84%.

Additionally, when operating in EV mode, emission levels were significantly higher than lab projections. This happened because electric motors were not strong enough to function independently, leading to engines using gasoline for nearly a third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed several large automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 more per year in running expenses than is assumed under lab conditions.

“The bold claims that automakers like to make about their PHEV vehicles are clearly far from the mark,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Hybrid vehicles have recently been drawn again into policy discussions as automakers have pressed the European Union to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from member states with significant car manufacturing.

Some high-level politicians have suggested PHEVs as a potential “compromise” option to include in the regulation.

One independent energy economics specialist, who was unaffiliated with the study, described the report a “highly valuable addition” after years in which parts of the car sector argued there was insufficient data to accurately evaluate actual emissions.

“These findings demonstrate, without question, that the gap between lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional cars,” the expert said. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of that evidence.”