Plug-in hybrid cars sold in Europe look clean on paper but produce far more CO2 in real driving, an analysis by Transport & Environment shows. Official figures for models sold between 2021 and 2023 list average tailpipe emissions at 35 grams of CO2 per kilometre; real-world measurements are “no less than four times higher” than that label, the group found.
The organisation based its findings on hundreds of thousands of vehicle measurements collected by the European Environment Agency (EEA). By contrast with plug-in hybrids’ advertised 35 g/km, battery-only cars are listed at 0 g/km and conventional petrol cars at about 134 g/km. Previous reviews by the European Court of Auditors and the European Commission reached similar conclusions: the WLTP test underestimates hybrid emissions, and the gap has grown between 2021 and 2023.
What the real-world data show
Owners use plug-in hybrids in electric mode much less often than assumed in official tests and drive them more on gasoline. Hybrids also tend to switch to the petrol engine on highways or under hard acceleration, limiting all-electric range.
Transport & Environment reports that even when operating in “electric mode,” the average plug-in hybrid still consumes about 3 litres of gasoline per 100 kilometres — roughly 68 g CO2 per km. The organisation warns that emissions remain higher in everyday driving than the laboratory labels indicate.
Regulatory changes and industry pushback
Starting this year the European Commission is adjusting the official inspection method to reflect that electric mode is used less often in practice. From 2027 a further correction will be introduced; regulators say the change will reduce, but not eliminate, the discrepancy between lab and on-road emissions, bringing hybrids closer to the gap seen with petrol and diesel cars.
The auto industry is lobbying in Brussels against tougher accounting for hybrids. Trade body ACEA successfully pushed for relaxed CO2 standards for 2025 and is pressing to retain the old method for counting battery use. In a letter to European Commission President Ursula von der Leyen, ACEA wrote that revising the calculation method “gives an advantage to our competitors.”
Transport & Environment’s Lucien Mathieu likened the situation to past emissions scandals: “This is the perfect recipe for another scandal. The auto industry is once again asking the EU to look the other way.”
Market and consumer consequences
Accounting for higher real-world emissions affects costs and consumer choices. In the Netherlands, the bpm tax on new cars is based on CO2 figures: a car with “paper” emissions of 35 g/km would incur 737 euros in purchase tax in 2024. Under the new calculation method planned for 2027 that same car’s tax would rise to about 4,985 euros.
Fully electric cars are not subject to the emissions charge and therefore become relatively more attractive. The figures feed into a broader political battle in Brussels over the pace of the shift to zero-emission vehicles.
At the end of this year the European Commission will review its plan to allow only zero-emission car sales from 2035, a cornerstone of the European Green Deal. ACEA says the 2035 ban is “no longer feasible” and would harm the competitiveness of European industry; some automakers report falling sales and plant closures, while Chinese manufacturers hold a surplus of electric cars and most batteries originate in China. Other companies, including Volvo and Fastned, are calling on the EU to keep the 2035 target.
