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Plug-in hybrid cars release nearly 5x greater planet-heating emissions than official figures show, according to a new analysis.

Widening Gap In Lab and Actual Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit organization. That differs significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Researchers studied data from in-vehicle energy use meters of 800,000 cars registered in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Actual emissions are rising, while official figures are falling,” stated a senior researcher involved in the report. “This discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery power compared to total distance. They found that only a quarter of driving was done in electric mode, while lab assumptions assumed over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than official estimates. That happened because electric motors were insufficiently powerful sufficient to function alone, leading to combustion motors burning gasoline for almost a third of the travel completed in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled several large carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 extra annually in running costs than is assumed under lab tests.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have lately been brought again into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car sector and opposition from member states with significant car industries.

Some high-level politicians have proposed PHEVs as a potential “flexibility” solution to include in the legislation.

One independent energy policy expert, who was not involved with the study, described the report a “very useful addition” after a long period in which segments of the car industry argued there was too little information to accurately assess actual CO2 output.

“These findings show, without question, that the difference in official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” they stated. “Any policy adjustments regarding PHEVs should be made with utmost care and in the light of this data.”