New EU real‑world data show that PHEVs emit six times more CO₂ in everyday use – pressure on utility‑factor reform rises
An analysis of roughly 220,000 plug‑in hybrid vehicles registered in the EU from the 2024 model year finds average real emissions of 145 g CO₂/km – six times the WLTP values of 24 g CO₂/km. The discrepancy fuels the upcoming debate on tightening the utility‑factor.
A new analysis of roughly 220,000 plug‑in hybrid vehicles (PHEVs) registered in the European Union from the 2024 model year reveals that real‑world CO₂ emissions average 145 g CO₂ per kilometre. That is six‑fold the official WLTP figure of 24 g CO₂/km. The figures come from a study by the NGO Transport & Environment, which draws on on‑board fuel‑consumption monitoring (OBFCM) data from the European Environment Agency (EEA).
Real emissions vs. WLTP – the numbers at a glance
The gap between laboratory and real‑world measurements has widened compared with the previous year. While in 2023 the average real emissions were 138 g CO₂/km and the WLTP figure was 28 g CO₂/km (a factor of five), the 2024 numbers stand at 145 g versus 24 g CO₂/km (a factor of six). By contrast, conventional combustion cars still emit an EU‑average of 169 g CO₂/km, meaning PHEVs are only about 14 % lower.
| Vehicle type | Real emissions 2024 | WLTP value 2024 | Factor (real/WLTP) |
|---|---|---|---|
| Plug‑in hybrid (PHEV) | 145 g | 24 g | 6,0 |
| Conventional combustion | 169 g | – | – |
Source: Heise – Plug‑in hybrids emit six times more CO₂ in everyday use than officially reported
Why the gap is widening
The analysis points to three main reasons for the growing discrepancy:
- WLTP values were reduced by about 15 % through larger battery capacities and optimised test conditions.
- Real emissions rose by roughly 5 % over the same period – an effect experts attribute to changed user behaviour.
- The utility‑factor (UF), which assumes the proportion of electric kilometres in the WLTP test, does not reflect the actual driving patterns of many PHEV owners.
Political consequences: the upcoming utility‑factor reform
The EU is preparing a two‑stage tightening of the utility‑factor for PHEVs – the first stage is slated to take effect in 2025, the second in 2027. The current analysis provides legislators with fresh evidence at the very moment the European Council will discuss the reforms in mid‑October 2026. Representatives of the auto industry and the German federal government have already voiced concerns that an overly strict adjustment could hinder the launch of new hybrid models.
An independent transport‑policy expert, who wishes to remain anonymous, explains: “The data show that the previous assumption about the electric driving behaviour of PHEV users is heavily overstated. Without adjusting the utility‑factor, the EU’s emission targets risk being missed.”
Outlook and need for action
The figures suggest that EU policy must lean more on real‑world driving data to achieve credible climate goals. In addition to adjusting the utility‑factor, further measures could be debated, such as stricter battery‑capacity requirements or mandatory real‑time emission monitoring on the road.
For consumers, the discrepancy means that the advertised CO₂ savings of PHEVs are often not realised in everyday use. Automakers such as BMW, Mercedes‑Benz, Audi and Volkswagen now face growing pressure to declare their hybrid models more transparently and to actually increase electric range.