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Plug-in hybrid cars emit almost 5x more global warming pollution than lab-reported data show, according to a new report.

Growing Gap In Lab and Real-World CO2 Output

Data shows that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy group. That contrasts significantly with laboratory estimates, which assumed a 75% decrease in emissions.

Analysts studied data from onboard fuel consumption monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “That gap is growing and poses a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to total mileage. The team determined that just a quarter of travel was done in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above official projections. This occurred because electric motors were not strong enough to operate independently, resulting to engines using fossil fuels for almost a third of the travel covered in electric mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several large carmaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 extra per year in operating costs than is assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV cars are clearly far from the truth,” commented a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought again into political debates as automakers have pressed the EU to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with significant automotive manufacturing.

Several high-level politicians have proposed plug-in hybrids as a potential “compromise” option to introduce in the regulation.

An independent energy policy expert, who was not involved with the study, called the report a “very useful addition” after years in which segments of the automotive industry claimed there was too little data to properly evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be made with extreme caution and in the light of that evidence.”