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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating pollution than official data indicate, as per a new report.

Widening Discrepancy In Lab and Real-World Emissions

Statistics reveals that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit group. That differs significantly with laboratory tests, which assumed a three-quarters reduction in emissions.

Analysts examined information from in-vehicle energy use monitors of 800,000 cars sold in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” stated a senior analyst involved in the study. “This discrepancy is growing and poses a significant issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in battery power compared to overall mileage. The team found that just a quarter of travel was completed in electric mode, whereas official estimates suggested 84%.

Additionally, when operating in electric mode, emission amounts were well above official estimates. This occurred because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors burning gasoline for almost a third of the travel completed in electric mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four large automaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 more per year in running costs than would be assumed under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have recently been brought again into policy discussions as automakers have lobbied the EU to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with significant automotive industries.

Some senior politicians have proposed PHEVs as a potential “flexibility” option to include in the regulation.

An independent energy economics expert, who was not involved with the study, called the analysis a “very useful addition” after years in which segments of the automotive industry claimed there was too little information to accurately assess real-world emissions.

“These findings show, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they said. “Any regulatory adjustments concerning PHEVs should be implemented with utmost caution and in the light of this data.”