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Plug-in hybrid cars emit nearly five times more global warming pollution than lab-reported data show, as per a new report.

Growing Discrepancy Between Lab and Actual Emissions

Statistics reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, according to research conducted by a non-profit organization. This contrasts significantly with lab estimates, which assumed a 75% decrease in emissions.

Analysts studied data from onboard energy use meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a lead analyst participating in the report. “That discrepancy is widening and creates a significant problem. As a result, PHEVs emit almost as much as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to overall mileage. They determined that just 27% of driving was completed in electric mode, whereas lab assumptions assumed 84%.

Additionally, when running in EV mode, emission amounts were well above official projections. This occurred because EV motors were not strong enough to function independently, leading to combustion motors using gasoline for nearly one-third of the distance covered in EV mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 extra annually in operating costs than is assumed under laboratory conditions.

“The bold claims that automakers often promote about their PHEV vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought back into policy discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant automotive industries.

Several high-level officials have proposed PHEVs as a possible “compromise” solution to introduce in the legislation.

An external energy economics specialist, who was not involved with the research, described the analysis a “very useful addition” after a long period in which segments of the automotive industry argued there was insufficient information to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert said. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of this evidence.”