🔗 Share this article

Plug-in hybrid electric vehicles emit almost five times greater planet-heating pollution than official figures show, according to a new analysis.

Widening Gap Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy organization. This differs significantly with lab tests, which assumed a 75% decrease in emissions.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a lead analyst involved in the study. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power compared to total mileage. The team found that only a quarter of travel was done in EV mode, whereas official assumptions suggested 84%.

Even, when operating in EV mode, emission levels were significantly higher than lab estimates. That occurred because EV motors were not strong sufficient to function independently, resulting to combustion motors using fossil fuels for nearly a third of the distance completed in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more per year in operating costs than would be estimated under laboratory tests.

“The strong statements that manufacturers like to make about their PHEV cars are obviously way off the truth,” stated a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy discussions as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and resistance from member states with significant car manufacturing.

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

One external energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which parts of the automotive sector argued there was too little data to accurately evaluate actual CO2 output.

“These findings show, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” they said. “All policy changes regarding PHEVs should be implemented with utmost care and considering that data.”