Plug-In Hybrids’ Real-World Emissions Are Six Times Higher

1. Transport & Environment reports that plug-in hybrids emit around six times more CO₂ in real-world driving than official tests suggest.

2. Real-world emissions reached 145g/km, compared with 24g/km in official tests.

3. This makes plug-in hybrids only 14% cleaner than conventional combustion cars.

Plug-in hybrid vehicles (PHEVs) are often promoted as a cleaner alternative to traditional petrol and diesel cars. They combine an electric battery with a combustion engine, allowing drivers to use electric power for shorter journeys. However, new European data suggests that their real-world emissions are much higher than official laboratory figures indicate.

According to analysis by Transport & Environment, plug-in hybrids registered in the EU in 2024 produced an average of 145 grams of CO2 per kilometre in real-world driving. Official tests, however, recorded only 24 grams per kilometre. This means that actual emissions were approximately six times higher than the figures used for regulatory and environmental assessments.

The gap has also widened compared with the previous year. In 2023, real-world emissions were reported at 138 grams of CO₂ per kilometre, while official tests recorded 28 grams. Although manufacturers claim that plug-in hybrid technology is improving, real-world emissions increased by around 5% in one year.

One reason for the difference is that laboratory tests assume frequent charging and significant use of electric power. In everyday driving, many owners may not charge their vehicles regularly or may use them for longer journeys than the tests assume. As a result, the petrol or diesel engine operates more often, increasing fuel consumption and emissions.

Transport & Environment argues that the EU should strengthen its testing rules rather than weaken them. The organisation says that plug-in hybrids produce only slightly fewer emissions than conventional combustion cars in real-world conditions. The findings highlight the importance of judging vehicles by how they perform on the road, not only by optimistic laboratory results.

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