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Plug-in hybrid cars release almost five times greater planet-heating emissions than lab-reported figures show, as per a new analysis.

Growing Gap Between Official and Actual Emissions

Statistics shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a non-profit organization. This differs sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Analysts studied data from in-vehicle energy use monitors of 800,000 cars registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” said a senior analyst involved in the study. “That gap is widening and creates a significant issue. Consequently, PHEVs pollute nearly as much as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power compared to total distance. They found that only 27% of driving was done in EV mode, while official estimates assumed over four-fifths.

Even, when operating in EV mode, pollution levels were well above official estimates. This happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors burning gasoline for nearly a third of the distance covered in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several large carmaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend about €500 extra annually in operating expenses than would be assumed under lab conditions.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn back into political discussions as carmakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and opposition from EU countries with large automotive industries.

Some high-level politicians have suggested PHEVs as a potential “compromise” option to include in the legislation.

One independent energy policy expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which parts of the car sector claimed there was too little information to accurately assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and considering this data.”