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Plug-in hybrid cars emit almost five times greater planet-heating emissions than lab-reported data indicate, as per a new analysis.

Growing Discrepancy In Official and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That contrasts significantly with lab estimates, which assumed a 75% reduction in pollution.

Researchers examined information from onboard energy use monitors of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” stated a senior researcher involved in the report. “That gap is growing and creates a significant problem. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles driven in battery power compared to overall mileage. The team found that just 27% of driving was completed in electric mode, whereas lab estimates suggested 84%.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. This happened because EV motors were insufficiently powerful enough to function independently, leading to combustion motors using fossil fuels for almost a third of the distance covered in electric mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output enabled four major automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more annually in running expenses than would be estimated under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” stated 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 better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Policy Discussion and Automotive Pressure

Hybrid cars have lately been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car manufacturing.

Several high-level officials have proposed PHEVs as a possible “compromise” option to include in the legislation.

An external energy economics specialist, who was not involved with the research, described the analysis a “very useful addition” after a long period in which segments of the automotive sector argued there was too little information to properly assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert stated. “All regulatory changes concerning PHEVs should be made with utmost caution and in the light of this data.”