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Plug-in hybrid electric vehicles release almost 5x more planet-heating emissions than lab-reported figures show, as per a new analysis.

Growing Discrepancy Between Official and Actual Emissions

Data shows that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit group. That differs sharply with lab tests, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of eight hundred thousand vehicles 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 official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a lead analyst participating in the report. “This gap is widening and creates a serious issue. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers linked most of the gap to inflated estimates of the “utility factor” – the percentage of miles travelled in electric power relative to total distance. They determined that just 27% of driving was done in electric mode, while official estimates suggested 84%.

Additionally, when running in EV mode, emission levels were well above lab estimates. That happened because EV motors were not strong enough to operate independently, leading to engines using fossil fuels for nearly one-third of the distance completed in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed four large carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

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

“The bold statements that automakers often promote about their PHEV cars are obviously way off the mark,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into policy discussions as carmakers have pressed the EU to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large automotive industries.

Several senior officials have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

An independent energy economics specialist, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was insufficient information to properly evaluate real-world emissions.

“These findings show, without question, that the difference between lab and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” the expert stated. “All policy changes regarding PHEVs should be made with utmost caution and considering that evidence.”