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Plug-in hybrid cars produce nearly five times greater global warming pollution than official figures show, as per a new report.

Widening Gap Between Official and Actual Emissions

Data reveals that PHEVs emit only 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit group. That contrasts significantly with lab tests, which suggested a three-quarters reduction in emissions.

Researchers studied information from onboard fuel consumption meters of 800,000 vehicles registered in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” stated a senior analyst involved in the report. “That gap is growing and creates a serious problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric mode relative to total distance. They determined that just a quarter of driving was done in EV mode, whereas lab assumptions suggested 84%.

Additionally, when operating in EV mode, emission levels were well above lab estimates. That happened because EV motors were insufficiently powerful enough to function independently, leading to engines burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 extra per year in running expenses than would be assumed under laboratory conditions.

“The bold statements that manufacturers often promote about their PHEV vehicles are clearly way off the mark,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn back into policy discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large car manufacturing.

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

One external energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which parts of the car industry argued there was too little data to accurately assess actual emissions.

“These findings demonstrate, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” they stated. “Any policy changes regarding PHEVs should be implemented with extreme care and considering this evidence.”