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Plug-in hybrid electric vehicles emit almost five times greater planet-heating emissions than lab-reported figures show, according to a recent analysis.

Widening Discrepancy Between Official and Actual Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis carried out by a advocacy organization. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Researchers studied information from onboard energy use meters of 800,000 cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” said a senior researcher involved in the study. “That gap is growing and poses a significant issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery mode compared to overall distance. The team found that only a quarter of travel was completed in EV mode, while official estimates suggested 84%.

Additionally, when operating in electric mode, emission levels were significantly higher than lab estimates. This occurred because EV motors were not strong enough to operate independently, leading to engines using fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output enabled several major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

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

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have recently been brought again into political debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with large automotive manufacturing.

Some high-level officials have proposed PHEVs as a possible “flexibility” option to include in the legislation.

An independent energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which segments of the car sector claimed there was too little data to accurately evaluate real-world emissions.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or conventional cars,” they stated. “All regulatory adjustments regarding PHEVs should be made with extreme care and considering that data.”