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Plug-in hybrid cars release almost five times more planet-heating emissions than official data show, according to a new analysis.

Widening Discrepancy In Lab and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy group. That differs sharply with lab tests, which suggested a 75% reduction in emissions.

Analysts studied information from onboard energy use meters of 800,000 vehicles registered in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a lead researcher participating in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to overall distance. The team determined that only a quarter of travel was done in electric mode, while official assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution amounts were well above official projections. That occurred because EV motors were insufficiently powerful enough to function independently, leading to combustion motors using fossil fuels for nearly one-third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV emissions enabled several major automaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more annually in operating costs than would be assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” stated a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been brought again into political discussions as carmakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large car industries.

Some senior officials have proposed plug-in hybrids as a possible “flexibility” option to include in the regulation.

One independent energy economics specialist, who was not involved with the research, described the report a “very useful addition” after a long period in which segments of the automotive sector argued there was insufficient data to accurately evaluate actual emissions.

“These findings demonstrate, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be made with extreme caution and considering this evidence.”