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Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than official data show, according to a recent report.

Widening Discrepancy In Official and Real-World CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. That differs significantly with lab tests, which suggested a 75% decrease in pollution.

Researchers examined information from onboard fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “This gap is growing and poses a serious problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Behind the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to overall mileage. The team determined that only a quarter of travel was completed in electric mode, while lab assumptions assumed over four-fifths.

Even, when operating in electric mode, pollution amounts were significantly higher than official projections. This happened because electric motors were not strong sufficient to function independently, leading to engines using gasoline for nearly a third of the travel covered in electric mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled four major carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 more annually in operating costs than would be assumed under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” stated a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn again into political debates as automakers have pressed the European Union 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 senior politicians have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

One independent energy economics expert, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which parts of the car industry argued there was insufficient data to properly assess actual CO2 output.

“The results demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be made with utmost caution and in the light of that evidence.”