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Plug-in hybrid cars emit nearly five times greater planet-heating pollution than official data indicate, as per a new analysis.

Growing Gap In Official and Real-World Emissions

Data shows that PHEVs release only 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a non-profit group. That contrasts sharply with lab tests, which suggested a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” stated a lead researcher involved in the report. “This discrepancy is widening and creates a serious problem. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery power relative to total mileage. The team determined that just 27% of travel was completed in electric mode, whereas lab estimates suggested 84%.

Additionally, when running in electric mode, emission amounts were significantly higher than lab estimates. This occurred because electric motors were not strong enough to operate alone, leading to engines burning gasoline for nearly one-third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed four large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 extra annually in running costs than would be estimated under lab conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn again into political debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant automotive industries.

Several senior officials have suggested PHEVs as a possible “flexibility” solution 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 argued there was insufficient information to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional cars,” they said. “Any regulatory changes regarding PHEVs should be made with utmost care and considering this evidence.”