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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating pollution than official data indicate, according to a new analysis.

Widening Discrepancy In Lab and Real-World Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, based on research conducted by a advocacy group. This differs sharply with lab estimates, which suggested a 75% decrease in pollution.

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

“Real-world emissions are rising, while official emissions are falling,” said a senior researcher involved in the report. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric power compared to overall mileage. They found that just a quarter of travel was done in electric mode, while official estimates assumed 84%.

Even, when running in electric mode, emission levels were well above official projections. This occurred because electric motors were not strong enough to operate independently, resulting to combustion motors using fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output allowed several large automaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 extra per year in running costs than is assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been drawn back into political debates as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with significant car manufacturing.

Some high-level politicians have suggested plug-in hybrids as a possible “compromise” option to introduce in the regulation.

An external energy policy expert, who was not involved with the research, described the analysis a “highly valuable addition” after a long period in which parts of the car industry claimed there was insufficient data to accurately assess actual CO2 output.

“The results show, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert stated. “All policy changes concerning PHEVs should be implemented with extreme caution and considering that data.”