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Plug-in hybrid cars emit almost 5x greater global warming emissions than lab-reported figures show, according to a recent analysis.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data shows that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a non-profit organization. That contrasts significantly with lab estimates, which suggested a 75% reduction in emissions.

Researchers studied data from onboard fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a lead analyst involved in the study. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total mileage. The team found that only a quarter of travel was done in electric mode, while lab estimates suggested over four-fifths.

Additionally, when running in EV mode, pollution amounts were significantly higher than lab projections. That happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors using gasoline for almost a third of the travel completed in electric mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions allowed four large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend about €500 extra per year in operating costs than would be assumed under lab conditions.

“The bold statements that manufacturers often promote about their PHEV vehicles are clearly far from the mark,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been drawn back into policy discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with significant automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “flexibility” option to include in the legislation.

An external energy policy expert, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which segments of the car industry claimed there was too little information to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with extreme care and in the light of that evidence.”