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Plug-in hybrid cars produce nearly 5x more planet-heating emissions than official data show, according to a new report.

Widening Discrepancy In Lab and Actual Emissions

Statistics reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel cars, based on analysis carried out by a non-profit organization. This differs sharply with laboratory tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard energy use meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” said a lead analyst involved in the study. “That discrepancy is growing and poses a significant issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Key Factors Behind the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of miles driven in battery power compared to total distance. They found that only 27% of driving was done in EV mode, while lab estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were well above official projections. This occurred because EV motors were insufficiently powerful enough to function alone, leading to engines burning gasoline for nearly a third of the travel completed in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output enabled several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would pay about €500 more per year in running costs than is estimated under laboratory tests.

“The bold statements that manufacturers like to make about their PHEV cars are clearly far from the truth,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn again into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from member states with significant car industries.

Several high-level politicians have proposed PHEVs as a potential “compromise” option to include in the regulation.

One independent energy policy expert, who was unaffiliated with the research, described the report a “highly valuable addition” after years in which segments of the car industry claimed there was insufficient data to accurately evaluate actual CO2 output.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel cars,” they stated. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering this data.”