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Plug-in hybrid cars produce nearly five times greater planet-heating pollution than official figures show, as per a new report.

Widening Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. That differs significantly with lab tests, which assumed a 75% decrease in pollution.

Analysts studied data from in-vehicle fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” said a senior researcher involved in the study. “That discrepancy is widening and creates a significant problem. Consequently, PHEVs emit almost as much as petrol cars.”

Primary Reasons Behind the Discrepancy

Researchers linked most of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to overall distance. They determined that just 27% of travel was done in EV mode, while official assumptions suggested over four-fifths.

Even, when operating in EV mode, emission levels were well above official estimates. This occurred because electric motors were not strong sufficient to function independently, resulting to combustion motors burning fossil fuels for nearly one-third of the travel covered in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four large automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay about €500 more per year in running costs than would be assumed under lab conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Hybrid cars have recently been brought again into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large automotive industries.

Some senior officials have proposed PHEVs as a potential “flexibility” option to introduce in the regulation.

An external energy policy specialist, who was unaffiliated with the research, called the analysis a “very useful addition” after a long period in which parts of the car sector claimed there was insufficient data to properly assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and in the light of this data.”