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Plug-in hybrid cars produce almost five times more global warming emissions than lab-reported figures indicate, according to a recent report.

Growing Discrepancy In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% less CO₂ than conventional gas and diesel cars, based on research carried out by a advocacy organization. That differs sharply with laboratory tests, which suggested a 75% decrease in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” stated a senior analyst participating in the study. “That discrepancy is growing and creates a serious issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to total mileage. The team found that only 27% of driving was done in electric mode, while official assumptions assumed over four-fifths.

Even, when operating in EV mode, emission levels were well above official estimates. That happened because electric motors were not strong sufficient to operate alone, resulting to combustion motors using fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several large automaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 extra per year in operating expenses than would be estimated under lab tests.

“The strong claims that automakers like to make about their PHEV vehicles are clearly far from the truth,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant automotive industries.

Some senior politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which segments of the automotive industry argued there was too little data to accurately assess real-world CO2 output.

“The results show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” they said. “All policy adjustments regarding PHEVs should be made with extreme care and considering this data.”