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Plug-in hybrid cars emit almost 5x more planet-heating pollution than lab-reported figures show, according to a recent report.

Widening Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a advocacy organization. That contrasts sharply with lab tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a senior analyst participating in the study. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs pollute almost as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery mode compared to overall distance. The team found that just a quarter of travel was completed in EV mode, while lab estimates suggested 84%.

Additionally, when running in EV mode, emission amounts were well above official projections. That happened because electric motors were not strong enough to operate independently, leading to engines using fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed several large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra annually in running costs than is estimated under laboratory tests.

“The strong statements that automakers often promote about their PHEV vehicles are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been brought back into policy debates as automakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant car manufacturing.

Some high-level officials have proposed PHEVs as a possible “flexibility” solution to include in the legislation.

An external energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after years in which segments of the automotive sector claimed there was too little data to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they stated. “Any regulatory changes concerning PHEVs should be made with extreme care and in the light of this data.”