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Plug-in hybrid cars produce nearly 5x greater global warming pollution than lab-reported data show, according to a new report.

Growing Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit organization. This differs significantly with lab tests, which assumed a three-quarters decrease in pollution.

Analysts examined information from onboard fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a lead analyst participating in the report. “That gap is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery power relative to overall distance. The team determined that just 27% of driving was completed in EV mode, while official estimates suggested over four-fifths.

Even, when running in electric mode, pollution amounts were significantly higher than official projections. That occurred because EV motors were insufficiently powerful enough to operate independently, leading to engines burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled several large automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra per year in running costs than would be estimated under lab tests.

“The bold statements that manufacturers often promote about their PHEV cars are clearly far from the truth,” stated a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been brought again into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large automotive industries.

Several senior officials have suggested plug-in hybrids as a possible “flexibility” solution to include in the legislation.

An independent energy economics specialist, who was unaffiliated with the research, described the analysis a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was too little information to properly assess actual CO2 output.

“These findings show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional cars,” the expert said. “All regulatory changes concerning PHEVs should be implemented with utmost caution and considering that evidence.”