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Plug-in hybrid electric vehicles emit nearly 5x greater planet-heating emissions than lab-reported figures show, according to a new analysis.

Growing Gap In Lab and Actual Emissions

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. That differs significantly with lab tests, which assumed a three-quarters decrease in emissions.

Analysts examined data from in-vehicle energy use monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a senior analyst involved in the report. “That gap is widening and poses a serious issue. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode relative to overall mileage. The team found that just a quarter of travel was completed in EV mode, while lab assumptions suggested 84%.

Additionally, when running in electric mode, pollution levels were well above lab projections. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to engines using fossil fuels for nearly a third of the travel completed in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions allowed several large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra per year in running costs than would be estimated under lab tests.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

Hybrid cars have recently been brought back into political discussions as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from EU countries with significant automotive industries.

Several senior politicians have proposed PHEVs as a potential “compromise” option to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which parts of the car sector argued there was insufficient information to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or conventional cars,” the expert stated. “All regulatory changes concerning PHEVs should be made with utmost care and in the light of that data.”