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Plug-in hybrid cars release almost five times greater global warming emissions than lab-reported figures indicate, as per a new analysis.

Widening Gap Between Official and Actual Emissions

Statistics shows that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. This differs sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Analysts studied information from onboard energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that actual 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 emissions are decreasing,” said a lead analyst involved in the report. “That discrepancy is widening and poses a serious issue. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Key Factors Driving the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power relative to overall distance. They determined that just a quarter of driving was completed in EV mode, while official estimates suggested 84%.

Additionally, when running in electric mode, emission levels were significantly higher than lab estimates. That occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to engines burning fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions enabled several large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra per year in running costs than is assumed under laboratory conditions.

“The strong claims that manufacturers like to make about their PHEV vehicles are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn again into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from EU countries with large automotive industries.

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

An external energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which segments of the car sector argued there was too little information to properly assess real-world emissions.

“These findings show, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or conventional cars,” they said. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering that evidence.”