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Plug-in hybrid cars release nearly 5x greater global warming pollution than official figures indicate, as per a recent report.

Widening Gap In Official and Actual Emissions

Data reveals that PHEVs emit only 19% less CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a non-profit organization. This contrasts sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead researcher participating in the study. “This gap is growing and poses a serious issue. Consequently, PHEVs emit almost as much as petrol vehicles.”

Key Reasons Behind the Discrepancy

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power relative to overall mileage. The team found that only a quarter of travel was done in EV mode, while official estimates assumed 84%.

Even, when running in EV mode, emission levels were well above official estimates. This occurred because electric motors were not strong enough to function alone, leading to combustion motors using gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions enabled four major automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

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

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into policy discussions as carmakers have pressed the EU to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with large automotive industries.

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

One external energy economics expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little data to properly evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” the expert stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme care and considering this data.”