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Plug-in hybrid cars emit nearly five times more planet-heating pollution than official figures show, as per a new report.

Widening Discrepancy In Lab and Actual Emissions

Statistics reveals that PHEVs emit only 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. This differs significantly with lab tests, which suggested a 75% reduction in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a lead analyst participating in the study. “This discrepancy is widening and poses a significant issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery power compared to total mileage. They determined that only a quarter of travel was completed in electric mode, while lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than lab estimates. This occurred because electric motors were not strong sufficient to operate alone, leading to combustion motors burning gasoline for nearly one-third of the distance completed in electric mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV emissions enabled four large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Additionally, 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 PHEV cars are clearly way off the truth,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid vehicles have recently been brought back into political debates as carmakers have lobbied the EU to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large automotive industries.

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

One external energy economics expert, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after years in which segments of the automotive industry claimed there was too little information to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme caution and in the light of that data.”