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PHEVs release nearly five times greater planet-heating pollution than lab-reported figures indicate, according to a new analysis.

Growing Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel cars, based on analysis conducted by a advocacy group. This contrasts sharply with lab tests, which assumed a three-quarters reduction in emissions.

Analysts examined information from in-vehicle fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” stated a senior analyst participating in the study. “That discrepancy is widening and creates a significant problem. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode compared to overall distance. They determined that just a quarter of driving was done in electric mode, while lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were well above lab estimates. That occurred because EV motors were insufficiently powerful enough to function independently, resulting to engines using fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 more per year in operating costs than would be estimated under laboratory conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have lately been drawn back into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and resistance from member states with large car manufacturing.

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

One independent energy policy specialist, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which segments of the automotive sector argued there was too little data to properly assess real-world emissions.

“These findings demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional cars,” they said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of that data.”