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Plug-in hybrid cars emit almost 5x more global warming emissions than lab-reported figures indicate, according to a new report.

Widening Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit group. This contrasts sharply with laboratory estimates, which suggested a three-quarters reduction in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 cars registered in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are falling,” stated a lead analyst involved in the report. “That gap is growing and poses a serious issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to overall mileage. They found that only a quarter of driving was done in electric mode, whereas official assumptions assumed 84%.

Additionally, when operating in EV mode, emission levels were significantly higher than official estimates. This occurred because EV motors were not strong enough to function independently, resulting to engines burning fossil fuels for nearly one-third of the distance covered in EV mode.

Regulatory and Financial Implications

Based on calculations, the underestimation of PHEV CO2 output allowed several large carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 extra per year in running costs than is estimated under laboratory tests.

“The strong claims that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant car industries.

Several senior politicians have suggested PHEVs as a possible “flexibility” solution to include in the legislation.

An external energy policy specialist, who was not involved with the research, called the analysis a “very useful contribution” after years in which segments of the car industry claimed there was insufficient data to properly assess actual emissions.

“These findings demonstrate, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” they stated. “All regulatory adjustments regarding PHEVs should be implemented with extreme care and in the light of that data.”