New real-world analysis suggests plug-in hybrid electric vehicles (PHEVs) may consume more fuel in everyday driving than official laboratory test figures indicate, underscoring the gap between certification cycles and how vehicles are actually used on the road.
Research from Germany’s Fraunhofer Institute for Systems and Innovation Research (ISI), in partnership with ifeu and Öko-Institut, examined real-world driving data from roughly one million PHEVs built between 2021 and 2023. The study found average fuel consumption of about 5.9 L/100 km in daily use, compared with laboratory ratings often cited at 1-2 L/100 km.
The difference appears largely tied to driving behaviour. Test-cycle values assume a high share of electric-only operation, but researchers found many vehicles operate in electric mode for a smaller portion of total kilometres travelled. When the combustion engine engages more frequently, fuel consumption rises accordingly.
The Guardian, which first reported on the findings, noted that real-world consumption averaged close to 6 L/100 km — roughly three times higher than certification figures derived under controlled testing conditions.
Researchers say the results highlight the importance of aligning regulatory assumptions with real driving patterns. As testing protocols evolve, particularly in Europe, policymakers are examining ways to incorporate more real-world data into emissions and fuel-economy assessments.
Understanding buyer charging habits and driving profiles could also shape satisfaction, resale values and long-term ownership costs.
