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PHEVs produce nearly five times greater global warming emissions than official data indicate, according to a recent analysis.

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs emit just 19% less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit group. This contrasts significantly with lab estimates, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are falling,” said a lead analyst participating in the report. “This discrepancy is widening and poses a significant issue. As a result, PHEVs emit nearly as much as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in electric power relative to overall mileage. The team found that just a quarter of driving was completed in electric mode, whereas lab estimates suggested over four-fifths.

Even, when operating in electric mode, emission amounts were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to engines using fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled four large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could pay about €500 more annually in running costs than would be assumed under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the mark,” stated a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant automotive manufacturing.

Some high-level officials have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

An external energy policy expert, who was not involved with the research, called the analysis a “very useful addition” after a long period in which segments of the car sector argued there was too little data to properly assess actual CO2 output.

“The results show, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” they stated. “Any policy adjustments concerning PHEVs should be made with utmost care and considering that evidence.”