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PHEVs produce almost 5x greater global warming emissions than lab-reported figures show, as per a new analysis.

Growing Gap Between Official and Actual Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. That contrasts sharply with laboratory tests, which assumed a 75% decrease in emissions.

Researchers studied data from in-vehicle energy use monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are decreasing,” stated a senior researcher participating in the study. “This discrepancy is widening and poses a serious problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in battery mode relative to total mileage. They found that only a quarter of driving was completed in electric mode, whereas official estimates suggested 84%.

Additionally, when running in EV mode, emission amounts were well above official projections. That happened because electric motors were not strong enough to function independently, resulting to engines burning gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed several large automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 more annually in running expenses than would be assumed under lab conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the mark,” commented a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought again into political discussions as carmakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large car manufacturing.

Some high-level politicians have proposed PHEVs as a possible “compromise” solution to introduce in the regulation.

An independent energy economics expert, who was not involved with the research, called the report a “very useful addition” after years in which parts of the automotive sector claimed there was insufficient information to accurately assess real-world emissions.

“These findings demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering this data.”