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PHEVs produce almost five times more planet-heating emissions than lab-reported figures show, according to a new report.

Widening Gap In Official and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a non-profit organization. This contrasts significantly with lab tests, which suggested a three-quarters reduction in emissions.

Analysts examined information from in-vehicle energy use meters of 800,000 vehicles registered in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are falling,” stated a lead researcher involved in the report. “This discrepancy is widening and creates a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to overall distance. The team found that just 27% of driving was completed in EV mode, while official assumptions suggested 84%.

Additionally, when running in electric mode, emission levels were significantly higher than official projections. This happened because electric motors were insufficiently powerful sufficient to operate independently, leading to engines using gasoline for nearly a third of the distance completed in electric mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV emissions allowed several major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would pay about €500 extra per year in operating costs than is estimated under laboratory tests.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Hybrid cars have recently been drawn back into policy debates as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car sector and resistance from member states with large automotive manufacturing.

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

One external energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which segments of the automotive sector argued there was insufficient information to properly evaluate actual emissions.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” they stated. “Any policy adjustments regarding PHEVs should be made with extreme caution and considering that data.”