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Plug-in hybrid electric vehicles produce nearly 5x more global warming pollution than lab-reported data show, according to a new analysis.

Widening Gap In Official and Actual Emissions

Data reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel vehicles, according to research conducted by a non-profit group. That differs significantly with lab estimates, which assumed a 75% decrease in emissions.

Researchers studied data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” stated a lead analyst involved in the study. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode relative to total mileage. The team found that only a quarter of driving was completed in electric mode, whereas lab estimates suggested 84%.

Additionally, when operating in EV mode, emission levels were well above official projections. That happened because EV motors were insufficiently powerful sufficient to operate alone, leading to combustion motors using fossil fuels for almost a third of the distance covered in electric mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output enabled four large carmaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra per year in operating costs than would be estimated under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are obviously far from the truth,” commented a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Hybrid cars have recently been drawn again into political debates as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from member states with significant automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “flexibility” option to introduce in the legislation.

One independent energy economics expert, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which segments of the automotive sector argued there was insufficient data to accurately assess actual emissions.

“The results show, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” they stated. “Any regulatory changes regarding PHEVs should be implemented with extreme care and considering this data.”