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Plug-in hybrid electric vehicles produce almost five times more global warming emissions than official figures show, according to a recent report.

Growing Gap In Lab and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a non-profit group. This contrasts sharply with laboratory estimates, which suggested a 75% reduction in pollution.

Analysts studied data from in-vehicle energy use meters of eight hundred thousand cars sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” said a senior researcher involved in the report. “That gap is widening and poses a serious problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to total mileage. The team determined that only a quarter of driving was completed in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when operating in electric mode, emission levels were well above official estimates. That occurred because electric motors were not strong enough to operate independently, resulting to engines using fossil fuels for almost one-third of the distance completed in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV emissions allowed several major automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in operating expenses than would be estimated under lab tests.

“The bold claims that automakers often promote about their PHEV cars are obviously way off the truth,” commented a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Debate and Automotive Pressure

Hybrid cars have recently been brought again into political debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large car manufacturing.

Several high-level officials have suggested PHEVs as a possible “flexibility” option to introduce in the legislation.

An independent energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which segments of the car sector claimed there was too little data to properly assess real-world CO2 output.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert said. “All policy changes concerning PHEVs should be made with extreme care and in the light of that data.”