Overview

• T&E reports that 2023 plug-in hybrid CO2 output was about 4.9 times higher in real driving than in laboratory tests, up from 3.5 times in 2021.
• In practice, PHEVs emit only about 19% less CO2 than petrol and diesel cars, far below WLTP assumptions that suggested a 75% cut.
• The gap is linked to overestimated utility factors, with real-world electric-mode use around 27% versus an official 84%, and engines operating for roughly one-third of ‘electric’ distance.
• Underreported emissions let four major carmaker groups avoid more than €5bn in EU fines between 2021 and 2023, according to the analysis.
• Drivers incur roughly €500 extra in annual running costs compared with lab-based estimates, intensifying debate over whether hybrids should be permitted after the EU’s 2035 zero-emission deadline.