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

Growing Gap Between Official and Actual CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy organization. This contrasts sharply with lab estimates, which suggested a 75% decrease in pollution.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a senior researcher involved in the report. “This discrepancy is widening and creates a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Factors Behind the Emissions Gap

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total mileage. The team found that just 27% of travel was done in EV mode, whereas official assumptions suggested over four-fifths.

Additionally, when running in electric mode, pollution levels were well above lab projections. This occurred because EV motors were insufficiently powerful enough to function independently, leading to combustion motors burning fossil fuels for nearly a third of the travel covered in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several major carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 extra per year in running expenses than would be estimated under laboratory conditions.

“The strong claims that automakers often promote about their PHEV cars are clearly far from the mark,” stated a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid cars have recently been drawn again into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large automotive industries.

Several senior politicians have suggested PHEVs as a possible “compromise” option to include in the regulation.

One independent energy economics expert, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the automotive sector claimed there was insufficient information to properly evaluate real-world emissions.

“The results demonstrate, without question, that the difference in lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” they said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and considering that evidence.”