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PHEVs release nearly 5x more planet-heating emissions than lab-reported figures show, according to a new report.

Growing Gap Between Lab and Real-World Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. That contrasts sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a lead analyst involved in the report. “That gap is growing and poses a significant problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in battery mode relative to total mileage. The team found that only a quarter of travel was completed in electric mode, whereas lab assumptions assumed 84%.

Even, when running in EV mode, emission amounts were significantly higher than lab projections. That occurred because EV motors were insufficiently powerful enough to function alone, resulting to combustion motors burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed several major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in running expenses than would be assumed under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid cars are clearly far from the mark,” commented a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and resistance from member states with significant automotive industries.

Several senior politicians have proposed PHEVs as a potential “flexibility” option to include in the regulation.

An independent energy policy expert, who was unaffiliated with the study, described the report a “very useful contribution” after years in which segments of the car industry argued there was too little data to properly evaluate real-world emissions.

“These findings show, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” they said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering this evidence.”