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Plug-in hybrid electric vehicles produce almost five times greater planet-heating pollution than official figures show, as per a recent report.

Widening Discrepancy Between Official and Real-World Emissions

Data reveals that PHEVs emit just 19% less CO₂ than conventional petrol and diesel cars, based on research conducted by a advocacy group. That differs sharply with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers studied information from onboard fuel consumption meters of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” stated a senior analyst participating in the report. “This gap is growing and creates a significant issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric mode compared to total mileage. The team determined that only 27% of travel was completed in EV mode, whereas lab assumptions suggested 84%.

Additionally, when operating in EV mode, pollution amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful sufficient to function alone, leading to combustion motors using gasoline for nearly one-third of the travel covered in electric mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would spend about €500 more per year in running expenses than would be assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously way off the truth,” stated a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have recently been drawn back into political debates as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant car manufacturing.

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

An independent energy economics specialist, who was not involved with the study, described the report a “very useful contribution” after a long period in which parts of the car industry argued there was insufficient information to properly evaluate real-world emissions.

“The results demonstrate, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” they stated. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of this data.”