Think Plug-In Hybrids Are a Clean Compromise?
Researchers say European PHEVs emit almost as much CO2 as gas cars, with real-world electric driving far below claimed levels.By Natalie NeffPublished: Oct 16, 2025 1:56 PM EDT
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Plug-in hybrid electric vehicles (PHEVs) have been promoted as a sort of middle ground between gasoline cars and full EVs, a stepping stone for those interested in extending fuel mileage and reducing their environmental impact but still wary about taking the full electric leap.
But a study by Transport & Environment, a European NGO that promotes sustainable transport, claims that PHEVs aren’t as green as advertised, at least not in the real world.
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The organization analyzed onboard data from more than 800,000 PHEVs registered in Europe between 2021 and 2023, finding real‐world carbon emissions are about 4.9 times higher than official lab tests indicate.
T&E says while many test protocols assume PHEVs reduce emissions by up to 75%, the data suggests they average just 19% less CO₂ than conventional gasoline or diesel vehicles.T&E
The problem lies with what’s known as the “utility factor,” the assumed amount of driving performed solely on electric power. Estimates based on testing protocols performed in lab settings put it at around 84%; T&E’s data indicates the real figure is closer to 27%.
That’s because even when the vehicle is supposedly in electric mode, the engine kicks in for nearly a third of those miles, says T&E, pushing emissions up further.
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The result is, according to T&E, that while official emissions levels appear to be going down, the reality is real‐world emissions are going up.
T&E’s analysis also flags the financial stakes: Automakers have avoided more than €5 billion ($5.8 billions) in fines for missing EU fleet CO2 targets by underreporting PHEV emissions.
Still, T&E wants to frame the situation by saying, “Plug-in hybrids pollute almost as much as petrol cars,” which is hardly the case as 19% is a significant improvement. And maybe enough for those looking to take baby steps on their way to a full EV life.
