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PHEVs produce almost 5x more global warming pollution than lab-reported figures indicate, according to a new analysis.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in pollution.

Analysts studied data from in-vehicle energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a lead researcher participating in the study. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in electric power relative to overall distance. They found that just a quarter of travel was done in electric mode, while lab assumptions suggested 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than official projections. This happened because electric motors were not strong enough to operate independently, leading to combustion motors burning gasoline for almost a third of the distance covered in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled several large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

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

“The strong claims that automakers often promote about their PHEV vehicles are clearly way off the mark,” stated a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have recently been brought again into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car industry and opposition from member states with significant automotive industries.

Several high-level politicians have proposed plug-in hybrids as a potential “compromise” option to introduce in the regulation.

One independent energy policy expert, who was not involved with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive sector claimed there was insufficient information to properly assess real-world emissions.

“The results show, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel cars,” they said. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and considering that evidence.”