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Plug-in hybrid electric vehicles release almost 5x more global warming emissions than official figures indicate, as per a new analysis.

Growing Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to research conducted by a non-profit organization. This contrasts sharply with lab estimates, which assumed a 75% decrease in pollution.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” said a lead analyst involved in the study. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as heavily as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to total mileage. The team determined that only a quarter of driving was completed in electric mode, while lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than official estimates. This happened because EV motors were insufficiently powerful sufficient to operate alone, leading to engines burning fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed four major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more per year in running costs than would be estimated under lab tests.

“The strong claims that automakers like to make about their PHEV vehicles are clearly way off the truth,” commented a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been brought again into political discussions as carmakers have pressed the EU to relax CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large car industries.

Several high-level officials have suggested PHEVs as a possible “compromise” option to introduce in the legislation.

One external energy economics specialist, who was not involved with the study, described the analysis a “highly valuable addition” after years in which segments of the car sector claimed there was too little data to accurately assess actual emissions.

“The results demonstrate, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” the expert said. “Any policy changes regarding PHEVs should be implemented with extreme caution and in the light of this evidence.”