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Plug-in hybrid electric vehicles emit almost five times more planet-heating pollution than lab-reported figures show, as per a recent analysis.

Growing Discrepancy In Official and Actual Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a non-profit organization. That differs significantly with lab estimates, which suggested a 75% reduction in emissions.

Analysts studied data from onboard fuel consumption monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” said a senior analyst participating in the study. “This gap is growing and poses a significant issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery power compared to total distance. The team found that only 27% of travel was completed in electric mode, whereas lab estimates suggested 84%.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. This happened because electric motors were not strong enough to function alone, resulting to engines burning fossil fuels for almost one-third of the distance covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled four major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 more annually in running costs than is assumed under laboratory tests.

“The bold claims that automakers like to make about their PHEV cars are clearly way off the mark,” commented a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid cars have recently been brought back into policy discussions as carmakers have lobbied the EU to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with large automotive industries.

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

One external energy economics specialist, who was not involved with the study, described the report a “very useful addition” after a long period in which segments of the car sector argued there was too little data to accurately assess actual emissions.

“The results show, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” they said. “Any policy adjustments regarding PHEVs should be made with extreme care and in the light of this evidence.”