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Plug-in hybrid electric vehicles release almost 5x more global warming emissions than official data indicate, as per a new analysis.

Growing Gap In Official and Real-World Emissions

Data shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel cars, according to analysis conducted by a non-profit group. That differs significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers examined information from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a senior analyst participating in the study. “That gap is growing and poses a significant issue. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery mode relative to total mileage. The team found that just a quarter of driving was done in EV mode, whereas official assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than official estimates. This occurred because electric motors were not strong sufficient to operate alone, leading to engines burning fossil fuels for almost a third of the distance completed in electric mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV emissions enabled several large carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more annually in running expenses than is assumed under lab tests.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Hybrid cars have recently been brought again into policy discussions as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large automotive manufacturing.

Several senior officials have suggested PHEVs as a possible “flexibility” option to include in the legislation.

An independent energy policy expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which segments of the automotive industry argued there was insufficient information to properly assess real-world CO2 output.

“The results demonstrate, without question, that the difference in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with extreme caution and considering this evidence.”