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PHEVs release nearly 5x more global warming pollution than official data indicate, as per a recent report.

Widening Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, based on analysis carried out by a non-profit group. That differs significantly with laboratory estimates, which suggested a 75% reduction in emissions.

Researchers examined information from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the study. “That discrepancy is growing and creates a serious problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to overall mileage. They found that only 27% of travel was completed in EV mode, while lab estimates assumed over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful sufficient to operate independently, leading to engines using fossil fuels for almost one-third of the distance completed in EV mode.

Regulatory and Economic Implications

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

Additionally, drivers of PHEVs would pay approximately €500 more annually in running expenses than is assumed under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy debates as automakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant car manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

An external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was insufficient information to accurately evaluate actual emissions.

“These findings demonstrate, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and in the light of that evidence.”