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Plug-in hybrid cars release nearly 5x more global warming emissions than official data show, according to a new report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit group. This contrasts significantly with laboratory tests, which suggested a 75% decrease in pollution.

Analysts examined data from in-vehicle energy use meters of 800,000 vehicles sold in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a lead researcher involved in the report. “That discrepancy is widening and creates a significant issue. As a result, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to total distance. They found that only 27% of travel was completed in electric mode, while official estimates suggested 84%.

Additionally, when operating in EV mode, emission levels were well above lab estimates. This happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines using gasoline for almost a third of the travel completed in EV mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV CO2 output allowed several major automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay approximately €500 more annually in operating costs than is assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have lately been brought again into political debates as carmakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced intense lobbying from the car sector and resistance from EU countries with significant car industries.

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

An external energy policy expert, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which parts of the automotive sector argued there was too little information to accurately assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel vehicles,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme caution and considering this data.”