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PHEVs produce nearly 5x more planet-heating pollution than official figures indicate, according to a new analysis.

Widening Gap In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research carried out by a non-profit group. That contrasts sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers studied information from in-vehicle energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a senior analyst involved in the study. “This gap is growing and creates a serious issue. Consequently, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to total mileage. The team determined that only a quarter of driving was done in EV mode, while official assumptions assumed 84%.

Even, when operating in electric mode, emission amounts were significantly higher than lab projections. That happened because electric motors were insufficiently powerful enough to operate alone, leading to engines using gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output allowed several major automaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could spend approximately €500 more annually in operating costs than would be assumed under lab conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly far from the mark,” stated a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have lately been brought back into policy debates as automakers have lobbied the EU to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with significant automotive industries.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One external energy policy specialist, who was not involved with the research, called the report a “very useful addition” after a long period in which parts of the car industry argued there was insufficient data to properly assess actual emissions.

“These findings demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert said. “All regulatory changes concerning PHEVs should be made with utmost care and in the light of that evidence.”