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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating emissions than official figures indicate, as per a recent analysis.

Growing Gap In Official and Real-World CO2 Output

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit group. That contrasts sharply with lab estimates, which assumed a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of 800,000 cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” said a senior analyst involved in the report. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery mode relative to total distance. They found that just a quarter of travel was completed in EV mode, whereas lab estimates assumed over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. This happened because EV motors were insufficiently powerful enough to function independently, resulting to engines burning gasoline for nearly one-third of the travel covered in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV emissions allowed several large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in operating costs than is estimated under laboratory tests.

“The strong claims that manufacturers like to make about their PHEV cars are clearly far from the mark,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn back into policy debates as automakers have pressed the European Union to weaken CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Several high-level officials have proposed plug-in hybrids as a possible “compromise” solution to include in the legislation.

One independent energy policy specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which segments of the car industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“The results show, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they said. “All policy adjustments concerning PHEVs should be made with extreme caution and in the light of that evidence.”