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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating emissions than lab-reported data show, as per a new analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel cars, according to research conducted by a advocacy group. This contrasts significantly with lab tests, which assumed a three-quarters decrease in emissions.

Analysts examined data from onboard energy use monitors of 800,000 vehicles sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a lead analyst participating in the report. “This discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Factors Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to total mileage. They found that just 27% of driving was done in EV mode, whereas lab assumptions assumed 84%.

Even, when operating in electric mode, emission levels were well above official projections. That occurred because electric motors were insufficiently powerful sufficient to function independently, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV emissions allowed four major carmaker groups to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 more annually in running costs than is estimated under laboratory tests.

“The strong statements that manufacturers often promote about their PHEV cars are clearly way off the mark,” stated a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from member states with significant car industries.

Some high-level officials have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

An independent energy economics specialist, who was not involved with the study, called the report a “very useful contribution” after years in which segments of the car sector claimed there was too little information to properly assess real-world emissions.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional cars,” they said. “Any policy changes concerning PHEVs should be implemented with utmost caution and in the light of that data.”