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Plug-in hybrid cars produce almost 5x greater global warming emissions than lab-reported figures indicate, as per a new analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, according to research conducted by a advocacy organization. That contrasts significantly with lab tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” said a senior analyst involved in the study. “This discrepancy is growing and poses a significant problem. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to overall mileage. The team determined that only a quarter of driving was completed in electric mode, while official estimates suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab estimates. This happened because EV motors were insufficiently powerful sufficient to function independently, leading to engines burning fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 extra per year in running expenses than would be assumed under lab tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large automotive industries.

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

An independent energy policy specialist, who was unaffiliated with the research, called the report a “very useful addition” after a long period in which segments of the automotive industry argued there was insufficient information to accurately assess actual emissions.

“The results show, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional vehicles,” the expert stated. “All regulatory adjustments regarding PHEVs should be made with utmost care and in the light of that data.”