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Plug-in hybrid cars emit nearly 5x more planet-heating pollution than lab-reported figures show, according to a new analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to research carried out by a advocacy organization. That differs significantly with lab estimates, which suggested a 75% reduction in emissions.

Analysts studied information from in-vehicle fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a senior researcher involved in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to total distance. The team found that only 27% of driving was done in EV mode, while lab assumptions suggested 84%.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. This happened because electric motors were not strong enough to function alone, resulting to combustion motors using fossil fuels for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled four major carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 extra per year in running costs than is assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid cars are obviously far from the truth,” stated a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn again into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant automotive industries.

Some senior politicians have suggested PHEVs as a potential “flexibility” solution to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient data to properly assess actual emissions.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and considering that data.”