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Plug-in hybrid cars release almost 5x more planet-heating emissions than lab-reported figures show, according to a new analysis.

Growing Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to research conducted by a non-profit organization. This contrasts sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied data from onboard energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a senior researcher participating in the study. “That gap is widening and creates a significant issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to total mileage. They determined that just 27% of travel was completed in electric mode, while lab assumptions suggested over four-fifths.

Even, when operating in EV mode, emission amounts were significantly higher than lab projections. That occurred because EV motors were not strong sufficient to operate independently, leading to combustion motors using fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled several large carmaker companies to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more per year in running costs than is assumed under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid cars have recently been drawn back into policy 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 pressure from the car industry and opposition from EU countries with large car manufacturing.

Several senior officials have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

An external energy policy specialist, who was not involved with the study, described the report a “highly valuable addition” after years in which parts of the car industry claimed there was insufficient data to properly assess real-world emissions.

“The results demonstrate, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” they said. “All policy adjustments concerning PHEVs should be made with extreme caution and considering this data.”