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PHEVs release nearly five times greater planet-heating pollution than lab-reported data show, according to a recent analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research carried out by a advocacy group. This differs sharply with lab estimates, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard energy use monitors 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 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” said a lead analyst participating in the report. “This gap is growing and poses a serious issue. Consequently, PHEVs pollute almost as much as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to total distance. They determined that just a quarter of driving was done in electric mode, whereas lab estimates suggested 84%.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. This happened because electric motors were not strong sufficient to function independently, resulting to engines burning gasoline for almost a third of the distance completed in EV mode.

Regulatory and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled several large automaker companies to escape more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in running expenses than would be estimated under lab conditions.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” stated a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been brought back into policy debates as automakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with significant automotive industries.

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

One independent energy policy expert, who was not involved with the research, called the analysis a “highly valuable addition” after a long period in which segments of the car sector claimed there was too little data to properly evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they said. “All regulatory changes regarding PHEVs should be implemented with utmost caution and considering this data.”