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Plug-in hybrid cars produce almost five times more global warming emissions than lab-reported data indicate, according to a recent report.

Growing Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs release only 19% lower CO₂ than conventional petrol and diesel vehicles, based on research carried out by a non-profit organization. That differs significantly with lab tests, which assumed a three-quarters reduction in pollution.

Analysts studied information from onboard energy use meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” stated a senior researcher participating in the report. “This gap is widening and creates a significant problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to total mileage. They found that only a quarter of driving was completed in electric mode, while lab estimates assumed 84%.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. This occurred because EV motors were insufficiently powerful enough to operate independently, leading to combustion motors using fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled four major automaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

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

“The strong statements that automakers often promote about their PHEV cars are clearly far from the mark,” stated a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought back into political debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with large automotive industries.

Several high-level politicians have proposed plug-in hybrids as a potential “compromise” option to introduce in the legislation.

An independent energy economics specialist, who was not involved with the research, described the report a “very useful contribution” after years in which segments of the car industry argued there was insufficient data to accurately evaluate real-world emissions.

“These findings show, without question, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” the expert said. “Any policy changes regarding PHEVs should be made with extreme caution and in the light of that evidence.”