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PHEVs produce nearly five times greater global warming emissions than lab-reported data show, as per a recent analysis.

Growing Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs release just 19% lower CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy organization. That differs sharply with lab estimates, which suggested a 75% reduction in emissions.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

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

Key Factors Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total mileage. They determined that only 27% of driving was done in EV mode, whereas official assumptions assumed 84%.

Additionally, when operating in EV mode, pollution amounts were well above official estimates. That happened because EV motors were not strong sufficient to operate independently, leading to engines burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled four major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 more per year in operating expenses than is assumed under lab tests.

“The bold claims that automakers like to make about their plug-in hybrid cars are clearly way off the truth,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with significant car manufacturing.

Several high-level officials have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

An independent energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector argued there was too little data to properly assess actual CO2 output.

“The results show, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” they said. “All regulatory adjustments concerning PHEVs should be made with utmost caution and considering that evidence.”