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

Growing Gap In Official and Actual Emissions

Statistics reveals that PHEVs release just 19% less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a advocacy group. This differs significantly with lab tests, which suggested a three-quarters decrease in pollution.

Analysts studied information from in-vehicle energy use monitors of 800,000 cars registered in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” stated a senior analyst involved in the study. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to overall distance. They found that just a quarter of driving was completed in EV mode, whereas official estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines burning gasoline for almost a third of the distance covered in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled four large automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

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

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have lately been brought back into political debates as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with large car industries.

Several high-level officials have proposed PHEVs as a possible “flexibility” option to include in the legislation.

One independent energy economics specialist, who was not involved with the research, called the analysis a “very useful contribution” after a long period in which segments of the car sector argued there was too little information to properly assess actual emissions.

“The results show, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be made with utmost care and in the light of this data.”