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

Widening Discrepancy In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That differs significantly with lab tests, which suggested a 75% reduction in emissions.

Analysts examined data from onboard energy use monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” said a senior analyst involved in the report. “That gap is widening and creates a significant problem. As a result, PHEVs pollute almost as heavily as petrol cars.”

Primary Reasons Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall mileage. The team found that only 27% of travel was done in EV mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, emission levels were well above lab projections. This happened because electric motors were insufficiently powerful sufficient to operate independently, leading to combustion motors using gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled four major carmaker groups to escape over €5bn in fines from 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 extra per year in running expenses than would be assumed under laboratory tests.

“The bold claims that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been brought again into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant car manufacturing.

Several high-level officials have proposed plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which segments of the car industry argued there was too little data to accurately evaluate real-world CO2 output.

“The results show, beyond any doubt, that the gap in lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel vehicles,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with utmost care and in the light of that evidence.”