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Plug-in hybrid electric vehicles release nearly five times greater planet-heating pollution than official figures indicate, according to a new report.

Growing Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, according to research carried out by a advocacy group. That contrasts sharply with lab estimates, which suggested a three-quarters decrease in emissions.

Analysts studied information from onboard energy use meters of 800,000 cars sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a lead analyst participating in the study. “That discrepancy is growing and poses a serious problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery power compared to overall distance. The team determined that just a quarter of travel was completed in EV mode, while lab assumptions suggested 84%.

Additionally, when operating in EV mode, pollution levels were well above official projections. That happened because EV motors were not strong sufficient to operate alone, leading to combustion motors using fossil fuels for nearly one-third of the travel completed in EV mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV emissions enabled four large automaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 extra per year in running costs than would be assumed under lab conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the truth,” stated a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been brought back into policy discussions as automakers have pressed the European Union to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large automotive industries.

Several senior officials have suggested PHEVs as a potential “compromise” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which parts of the car industry claimed there was insufficient information to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” they said. “All policy changes concerning PHEVs should be made with utmost caution and considering this data.”