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PHEVs produce almost 5x more planet-heating pollution than lab-reported data show, according to a new report.

Growing Discrepancy In Official and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel cars, based on research conducted by a non-profit organization. That contrasts significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Analysts examined data from in-vehicle energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” said a lead researcher participating in the study. “That discrepancy is widening and creates a significant issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to overall distance. The team determined that just a quarter of driving was done in EV mode, while lab assumptions assumed over four-fifths.

Even, when running in EV mode, emission levels were well above official projections. That happened because electric motors were not strong sufficient to operate independently, resulting to engines using fossil fuels for almost a third of the travel completed in EV mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed several large automaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more per year in operating costs than is assumed under laboratory tests.

“The bold claims that automakers often promote about their PHEV cars are obviously far from the truth,” stated a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been brought back into political debates as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with large car manufacturing.

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

An independent energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful addition” after a long period in which segments of the car sector claimed there was insufficient information to accurately evaluate actual emissions.

“These findings demonstrate, without question, that the difference between official and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel vehicles,” they stated. “Any regulatory changes regarding PHEVs should be implemented with utmost caution and considering this evidence.”