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PHEVs release nearly five times greater planet-heating pollution than official figures indicate, according to a new report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit just 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. This contrasts sharply with lab tests, which assumed a three-quarters reduction in emissions.

Analysts studied information from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a lead analyst involved in the study. “That gap is widening and poses a significant problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed most of the difference to overestimates of the “utility factor” – the percentage of miles travelled in electric power compared to overall mileage. They determined that only 27% of driving was completed in electric mode, while official assumptions suggested 84%.

Even, when operating in EV mode, emission amounts were well above official projections. That happened because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors burning gasoline for almost one-third of the distance covered in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled several major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 more per year in running costs than is assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the truth,” stated a automotive analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been drawn back into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with significant car industries.

Several high-level politicians have suggested plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to properly assess actual CO2 output.

“The results demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they said. “All regulatory changes regarding PHEVs should be implemented with extreme care and considering this evidence.”