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Plug-in hybrid cars produce almost 5x more planet-heating pollution than official figures show, as per a recent analysis.

Widening Gap In Lab and Real-World CO2 Output

Data shows that PHEVs emit only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit organization. That contrasts significantly with laboratory tests, which assumed a 75% decrease in emissions.

Analysts studied information from in-vehicle energy use meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a lead analyst involved in the report. “This gap is widening and poses a serious problem. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery power relative to total mileage. The team found that just a quarter of travel was completed in EV mode, whereas official assumptions suggested over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than official estimates. That occurred because electric motors were not strong sufficient to function independently, leading to combustion motors burning fossil fuels for almost a third of the distance covered in electric mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four large automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend about €500 extra annually in running expenses than would be assumed under laboratory tests.

“The bold statements that automakers like to make about their PHEV cars are clearly far from the truth,” commented a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn back into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant car manufacturing.

Some senior officials have proposed PHEVs as a potential “compromise” solution to introduce in the regulation.

An independent energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient information to accurately assess real-world CO2 output.

“The results show, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel cars,” the expert said. “All policy adjustments regarding PHEVs should be implemented with utmost caution and considering that evidence.”