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PHEVs emit almost 5x more global warming emissions than lab-reported figures indicate, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a non-profit organization. This contrasts significantly with laboratory tests, which suggested a 75% decrease in emissions.

Researchers studied data from onboard energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” said a lead researcher involved in the report. “This gap is widening and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to total distance. They found that only 27% of driving was completed in EV mode, whereas official assumptions assumed 84%.

Additionally, when operating in electric mode, pollution amounts were well above lab estimates. That happened because electric motors were not strong sufficient to operate alone, leading to engines burning fossil fuels for nearly a third of the distance completed in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed four large automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 more per year in running costs than would be assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly 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 saving money. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and opposition from EU countries with large automotive manufacturing.

Some high-level officials have proposed PHEVs as a potential “compromise” option to include in the regulation.

One external energy policy expert, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which segments of the automotive sector claimed there was too little information to accurately evaluate actual CO2 output.

“The results show, without question, that the difference in lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” they stated. “All regulatory adjustments regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”