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Plug-in hybrid cars release almost 5x greater planet-heating pollution than official figures indicate, as per a recent report.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit organization. This differs significantly with laboratory tests, which suggested a 75% decrease in pollution.

Researchers studied data from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a lead analyst participating in the report. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Primary Reasons Behind the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery power relative to total mileage. The team determined that only a quarter of travel was completed in EV mode, while official assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than official estimates. This occurred because EV motors were not strong enough to function independently, resulting to engines burning fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ standards.

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

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Hybrid cars have recently been drawn again into political discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large automotive industries.

Several high-level politicians have proposed PHEVs as a possible “compromise” option to introduce in the legislation.

An independent energy economics expert, who was unaffiliated with the study, called the report a “very useful contribution” after years in which parts of the automotive industry argued there was insufficient information to accurately evaluate real-world emissions.

“These findings demonstrate, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be made with utmost care and considering this data.”