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Plug-in hybrid cars release nearly five times greater global warming emissions than official figures show, as per a new analysis.

Widening Gap Between Lab and Real-World Emissions

Data shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy group. This differs significantly with lab tests, which assumed a 75% decrease in emissions.

Researchers examined information from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” stated a senior researcher participating in the study. “This discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric power relative to total distance. They found that just a quarter of travel was done in electric mode, while lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution amounts were well above lab projections. That happened because electric motors were insufficiently powerful enough to function alone, leading to engines using gasoline for almost one-third of the travel covered in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several major automaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more annually in operating expenses than is estimated under lab conditions.

“The bold statements that automakers like to make about their PHEV vehicles are obviously far from the mark,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Hybrid cars have lately been brought back into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with significant car manufacturing.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” option to introduce in the legislation.

One external energy policy expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which parts of the automotive sector claimed there was too little information to properly assess real-world CO2 output.

“These findings show, without question, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel cars,” they stated. “Any policy changes concerning PHEVs should be implemented with utmost care and considering that data.”