Real-world CO₂ emissions from European plug-in hybrid electric vehicles (PHEVs) ran at 4.6 times official values for 2023 registrations, up from 3.5 times for those registered in 2021, according to research covering nearly 920,000 vehicles. The widening gap reflects declining real-world electric driving rates across models with increasing electric range, contradicting the assumptions built into the official test cycle.

The International Council on Clean Transportation (ICCT) attributed the widening to the European Union (EU) utility factor (UF) formula. The formula links official CO₂ ratings to an assumed electric driving share set at 80%, while data from the study put the real-world figure at around 21% for 2022.

Jan Dornoff, Research Lead at the ICCT and the study’s author, said: “Plug-in hybrids registered in 2023 emitted almost 5 times more CO₂ on the road than their official values suggest, and the discrepancy has grown over the years. This matters for how these vehicles count toward manufacturers’ CO₂ targets. Because the low emission values credited to plug-in hybrids are rarely actually achieved on the road, these vehicles receive an unjustified advantage over combustion engine vehicles.”

PHEVs held around 10% of new European registrations between January and July 2026, while fully electric vehicles reached 22%. Chinese manufacturers held 28% of the PHEV segment, up 60% year-on-year; BYD recorded the highest PHEV share of its own European registrations at 60%, against 17% for Mercedes-Benz, 13% for BMW, and 12% for Volkswagen. The European Commission has scheduled a UF correction for 2027.

Source: ICCT