Plug-in hybrids pollute almost as much as petrol cars, according to new data from the EU.
PHEVs emit just 19% less CO2 per km, on average, than petrol and diesel cars, according to the data
The study by Transport & Environment of 127,000 PHEVs found they emit far more CO2 than claimed and the extra fuel consumed costs the average driver €500 (£435) a year.
The analysis reveals that PHEVs emit just 19% less CO2 per km, on average, than petrol and diesel cars.
PHEVs are supposed to save on emissions and fuel by switching between a battery, which is recharged by being plugged in, and a petrol or diesel engine. But in the real world, CO2 emissions from plug-in hybrids are almost five times what official tests suggest. The real-world data differs hugely from the official ‘WLTP’ tests where vehicles are driven in a way that regulators consider to be normal.
In the real world, plug-in hybrids emit 135g of CO2 per km on average, according to T&E analysis of data gathered by the European Environment Agency (EEA) from fuel monitors on the 127,000 vehicles that it tested, which were registered in 2023. Petrol and diesel cars emit 166g of CO2/km on average.
Even when driven in electric mode, PHEV engines consume three litres of petrol per 100km, on average, the EEA data shows. As a result, they emit 68g of CO2/km in electric mode – 8.5 times as much as official tests claim. This is because the electric motors in PHEVs generally have insufficient power for higher speeds or steep inclines and the engine needs to kick in. On average, the engine supplies power during almost one-third of the distance driven in electric mode, according to the data.
PHEVs cost drivers €500 more a year than claimed to fuel and charge because of the hidden fuel consumption in both electric and engine modes, the report also finds. Not only are plug-in hybrids expensive to drive, they are also more expensive to buy than clean alternatives. The average selling price of PHEVs in Germany, France and the UK in 2025 is €55,700, according to Bloomberg Intelligence. This is €15,200 higher than the average price of a battery electric car.
Lucien Mathieu, cars director at T&E, said: “Plug-in hybrids are one of the biggest cons in automotive history. They emit almost as much as petrol cars. Even in electric mode they pollute eight times as much as official tests claim. Technology neutrality cannot mean ignoring the reality that, even after a decade, PHEVs have never delivered.”
The study also indicates that PHEV emissions are increasing because of the trend towards longer electric ranges – as bigger batteries make the vehicles heavier and, therefore, burn more fuel in engine mode. These heavier vehicles also consume more energy than smaller cars when driven on the battery. Plug-in hybrids with an electric range above 75km actually emit more CO2 on average than those with a range between 45 and 75km (28-47 miles), the data shows.
Mercedes-Benz has the biggest gap between its official and real-world PHEV emissions, according to the 2023 data, emitting 494% more, on average. Its GLE-Class has the highest real-world emissions gap of cars sold that year, exceeding its official value by 611%. The other major European carmakers emitted around 300% more than their official CO2 ratings.
The European car industry is campaigning to be allowed to sell PHEVs after the EU’s 2035 deadline for zero-emission cars.
Carmakers are also demanding that the EU cancel the ‘utility factors’ – which represents the assumed share of driving done by PHEVs in electric mode – it has set to correct the CO2 rating of plug-in hybrids. The utility factors set for 2025 and 2027 gradually correct the gap between official and real-world emissions, meaning carmakers’ EU CO2 targets get stricter, pushing manufacturers to sell more battery electric cars.
Lucien Mathieu said: “Weakening the rules for plug-in hybrids is like drilling a hole in the hull of Europe’s car CO₂ law. Instead of steering the market toward affordable zero-emission cars, carmakers will flood it with expensive, polluting PHEVs. That risks sinking the EV investment certainty the market desperately needs.”
The UK’s Energy and Climate Intelligence Unit (ECIU), a non-profit organisation that supports informed debate on energy and climate change issues, said the research showed consumers were being “duped” by PHEVs.
Colin Walker, head of transport, commented: “In reality, PHEVs are little better than regular petrol and diesel cars when it comes to the fuel they consume, the CO2 they produce and the money they cost to run.
“However, the Government has recently weakened its EV sales targets, which could incentivise the sale of PHEVs at the expense of EVs. Given how much more fuel these vehicles burn than their manufacturers claim, the cost of this decision to the environment and to drivers’ wallets could be significant. Pushing the sale of vehicles which burn five times more fuel than their manufacturers claim certainly has echoes of the infamous Dieselgate scandal.
“Rather than distracting people with this outdated and expensive technology, the Government and car manufacturers could instead focus on helping regular families make the move to EVs – which, besides offering genuine reductions in greenhouse gas emissions, are capable of saving their owners hundreds, even thousands, of pounds a year in running costs.”