Overview
- The International Council on Clean Transportation used millions of on‑board fuel readings and registration data to estimate that plug‑in hybrid vehicles in the EU emitted roughly 100 million tonnes more CO2 between 2021 and 2025 than manufacturers' test-based figures imply.
- ICCT found real‑world CO2 for plug‑in hybrids was about four to five times higher than official values on average, with the discrepancy rising from 2021 to 2023 and some brands showing much larger gaps.
- Three main causes explain the gap: owners charge PHEVs far less than regulators assume, the combustion engine often assists during so‑called electric driving, and carrying two drivetrains raises fuel use.
- Policy response is contested: the European Commission adjusted the regulatory 'utility factor' in 2025 and plans a further correction in 2027, while the German federal government has publicly opposed the 2027 tightening despite an internal environment ministry study reaching similar findings.
- The scale matters for people and climate because PHEVs made about 9% of EU new car registrations in 2025 and are common as company cars when employers pay fuel but not charging, a mix that reduces electric kilometres and can let manufacturers meet fleet targets without cutting real emissions.