Plug-in Hybrid Vehicles Pollute Almost as Heavily as Petrol Cars, Study Finds

PHEVs emit almost 5x more global warming emissions than lab-reported figures show, according to a recent report.

Widening Discrepancy Between Official and Actual CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit group. That differs significantly with laboratory estimates, which suggested a three-quarters decrease in emissions.

Researchers studied data from onboard fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a senior researcher participating in the study. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric power relative to overall mileage. The team determined that only 27% of driving was completed in EV mode, while lab estimates assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were well above official projections. This happened because electric motors were not strong enough to operate independently, leading to engines burning gasoline for nearly a third of the distance covered in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled several major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 extra per year in operating costs than is assumed under lab conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously far from the truth,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn back into political discussions as automakers have lobbied the EU to weaken CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant car industries.

Several senior politicians have suggested PHEVs as a potential “flexibility” solution to include in the legislation.

An external energy economics expert, who was not involved with the research, called the analysis a “highly valuable addition” after a long period in which segments of the car industry claimed there was insufficient information to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel cars,” they said. “All policy adjustments concerning PHEVs should be implemented with extreme care and in the light of this data.”