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Plug-in hybrid cars produce nearly 5x greater global warming emissions than lab-reported figures show, as per a new report.

Growing Gap In Official and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit organization. This differs sharply with laboratory estimates, which suggested a 75% decrease in emissions.

Analysts examined information from onboard energy use meters of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” stated a lead researcher involved in the report. “That gap is widening and creates a significant problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in electric mode compared to overall mileage. They determined that just 27% of driving was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when running in EV mode, emission levels were well above lab estimates. This occurred because electric motors were not strong sufficient to function independently, resulting to combustion motors burning gasoline for nearly one-third of the travel covered in electric mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed four major carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 extra annually in running costs than is assumed under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid cars are clearly far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into policy discussions as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from EU countries with large automotive industries.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One external energy economics specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive sector claimed there was too little data to accurately evaluate real-world emissions.

“These findings show, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be implemented with utmost care and considering this data.”