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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating emissions than official data indicate, according to a new report.

Growing Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a advocacy group. This contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in emissions.

Analysts studied data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” stated a senior researcher involved in the study. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of miles driven in electric mode compared to total mileage. The team found that just 27% of driving was done in EV mode, whereas official estimates suggested 84%.

Additionally, when running in EV mode, pollution levels were well above lab projections. This occurred because electric motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for nearly a third of the travel covered in electric mode.

Regulatory and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled several major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 more annually in operating costs than would be estimated under lab tests.

“The strong claims that manufacturers often promote about their PHEV vehicles are obviously far from the mark,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving money. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into political debates as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with large car manufacturing.

Several senior officials have suggested PHEVs as a possible “flexibility” option to include in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, described the report a “very useful addition” after years in which segments of the car industry argued there was insufficient information to accurately evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” they stated. “All regulatory adjustments concerning PHEVs should be made with utmost caution and in the light of this evidence.”