🔗 Share this article

Plug-in hybrid cars emit nearly 5x greater planet-heating pollution than official figures indicate, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Data reveals that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit group. That differs sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers examined data from in-vehicle energy use meters of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” said a senior analyst participating in the report. “This gap is widening and poses a significant issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Behind the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power relative to overall mileage. The team determined that just a quarter of driving was completed in electric mode, whereas lab assumptions suggested 84%.

Even, when operating in EV mode, emission levels were well above official projections. That happened because electric motors were not strong enough to operate alone, leading to engines burning gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions allowed several large carmaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in running expenses than is assumed under laboratory tests.

“The bold claims that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Political Discussion and Automotive Pressure

Hybrid vehicles have recently been brought again into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and opposition from member states with large car industries.

Some high-level officials have proposed plug-in hybrids as a potential “flexibility” solution to include in the legislation.

An external energy economics specialist, who was not involved with the study, called the report a “very useful addition” after a long period in which parts of the automotive industry argued there was insufficient data to accurately assess real-world CO2 output.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” they said. “Any regulatory changes regarding PHEVs should be implemented with extreme care and in the light of that evidence.”