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

Growing Gap In Lab and Actual Emissions

Data reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit organization. This differs significantly with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts studied data from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” said a senior researcher participating in the study. “That gap is growing and poses a serious problem. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to total distance. The team found that just a quarter of travel was completed in EV mode, while lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were well above official estimates. This happened because EV motors were insufficiently powerful sufficient to function alone, leading to engines burning gasoline for almost a third of the distance completed in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions enabled several large automaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

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

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with significant car industries.

Several high-level officials have proposed PHEVs as a potential “compromise” option to include in the legislation.

An external energy economics specialist, who was unaffiliated with the study, called the analysis a “very useful contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to accurately assess actual CO2 output.

“These findings show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”