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PHEVs produce almost 5x more planet-heating pollution than official data show, according to a new report.

Growing Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit organization. This contrasts sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from onboard energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a lead analyst involved in the study. “That gap is widening and poses a significant problem. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to overall mileage. They determined that just a quarter of driving was completed in EV mode, whereas official estimates suggested 84%.

Additionally, when running in EV mode, pollution levels were significantly higher than official estimates. This happened because EV motors were insufficiently powerful enough to operate alone, resulting to engines burning fossil fuels for almost one-third of the travel covered in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV emissions allowed four major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more annually in operating expenses than is estimated under lab tests.

“The strong statements that manufacturers often promote about their PHEV cars are clearly far from the mark,” stated a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid cars have recently been drawn again into policy discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with significant car manufacturing.

Several high-level politicians have proposed PHEVs as a potential “compromise” solution to include in the regulation.

An external energy policy expert, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was insufficient information to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with utmost care and considering this data.”