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PHEVs produce nearly 5x more global warming pollution than lab-reported figures show, according to a new report.

Growing Gap Between Official and Actual CO2 Output

Data reveals that PHEVs release just 19% lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy group. That contrasts sharply with lab estimates, which suggested a 75% reduction in pollution.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a senior researcher involved in the study. “This discrepancy is growing and creates a serious issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Driving the Discrepancy

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to overall mileage. The team found that only 27% of driving was completed in electric mode, whereas lab assumptions suggested over four-fifths.

Even, when running in EV mode, pollution levels were well above lab projections. This happened because EV motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for almost one-third of the travel covered in EV mode.

Regulatory and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several major carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more per year in operating costs than is estimated under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been brought back into political debates as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant automotive manufacturing.

Some high-level officials have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

An external energy economics specialist, who was not involved with the research, described the analysis a “very useful contribution” after years in which parts of the automotive sector argued there was too little information to properly assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with utmost care and in the light of this evidence.”