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PHEVs emit almost 5x greater global warming emissions than official data indicate, according to a new report.

Growing Discrepancy Between Lab and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to research conducted by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a 75% decrease in pollution.

Researchers studied data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in the EU from 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.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery power compared to total mileage. The team found that only a quarter of travel was done in electric mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. This happened because electric motors were insufficiently powerful enough to function alone, resulting to engines burning gasoline for nearly a third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV emissions allowed four large automaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 extra per year in operating costs than would be assumed under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are clearly way off the mark,” commented a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into policy discussions as automakers have pressed the EU to relax CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car manufacturing.

Some high-level officials have proposed plug-in hybrids as a possible “compromise” option to include in the legislation.

An external energy economics specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which parts of the automotive sector argued there was too little information to accurately evaluate real-world CO2 output.

“The results show, without question, that the difference between lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” they stated. “Any policy changes regarding PHEVs should be made with utmost caution and considering that evidence.”