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Plug-in hybrid cars produce almost 5x greater planet-heating emissions than official figures indicate, according to a recent report.

Widening Gap Between Official and Actual CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel vehicles, according to research conducted by a advocacy organization. That contrasts significantly with lab tests, which assumed a three-quarters reduction in emissions.

Analysts studied data from in-vehicle energy use meters of eight hundred thousand cars registered in the EU between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a senior researcher participating in the study. “This gap is widening and poses a significant problem. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to total mileage. They determined that only a quarter of travel was completed in EV mode, whereas lab assumptions assumed 84%.

Even, when running in EV mode, emission levels were well above lab estimates. That happened because electric motors were insufficiently powerful enough to function alone, resulting to engines burning fossil fuels for nearly one-third of the distance completed in EV mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 more annually in running expenses than is assumed under laboratory tests.

“The strong statements that automakers like to make about their PHEV cars are obviously far from the truth,” commented a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into political discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with significant car manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

One external energy policy expert, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after years in which segments of the car sector argued there was insufficient information to accurately assess actual emissions.

“These findings show, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” they said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering this evidence.”