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Plug-in hybrid cars emit almost five times greater global warming emissions than official data show, according to a recent report.

Growing Gap Between Official and Actual CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. That differs sharply with lab estimates, which suggested a 75% reduction in emissions.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead analyst involved in the study. “That gap is widening and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery power relative to total distance. The team determined that only 27% of driving was done in EV mode, while lab estimates suggested over four-fifths.

Even, when operating in electric mode, pollution amounts were significantly higher than lab estimates. That occurred because electric motors were not strong enough to function alone, leading to combustion motors using gasoline for nearly a third of the distance covered in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV emissions allowed several large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in running expenses than would be estimated under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously way off the mark,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Hybrid cars have recently been brought again into policy discussions as automakers have lobbied the EU to relax CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with significant automotive industries.

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

One external energy economics expert, who was not involved with the study, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was insufficient data to properly evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” they stated. “Any regulatory changes concerning PHEVs should be implemented with utmost care and considering that data.”