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Plug-in hybrid cars emit nearly 5x greater global warming emissions than official data show, according to a recent report.

Widening Discrepancy In Official and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy organization. That differs significantly with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers examined information from in-vehicle energy use meters of 800,000 cars sold in Europe between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” stated a lead researcher involved in the study. “This gap is growing and creates a significant problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery power compared to total mileage. The team found that just a quarter of travel was done in electric mode, whereas lab estimates suggested over four-fifths.

Even, when running in electric mode, pollution amounts were well above lab estimates. This occurred because EV motors were not strong enough to function independently, resulting to engines using gasoline for almost one-third of the distance covered in EV mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed several major automaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 more annually in operating expenses than would be assumed under laboratory tests.

“The strong statements that manufacturers like to make about their PHEV cars are obviously way off the truth,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have recently been drawn back into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with significant car manufacturing.

Some senior politicians have suggested plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which segments of the automotive sector argued there was insufficient information to accurately assess actual emissions.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert said. “All regulatory changes concerning PHEVs should be made with utmost care and in the light of that evidence.”