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Plug-in hybrid electric vehicles release almost five times more global warming emissions than official data indicate, according to a recent analysis.

Widening Discrepancy In Official and Actual CO2 Output

Data shows that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, based on analysis conducted by a non-profit organization. This contrasts sharply with laboratory tests, which assumed a 75% reduction in emissions.

Analysts examined data from onboard energy use meters of 800,000 vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a senior analyst participating in the report. “That gap is widening and creates a significant problem. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Researchers linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to overall mileage. They determined that just 27% of driving was done in EV mode, while official estimates suggested 84%.

Even, when running in EV mode, pollution levels were significantly higher than lab projections. That happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to engines using fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled several large carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could spend about €500 extra annually in running costs than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Industry Pressure

Hybrid cars have lately been drawn again into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive manufacturing.

Several high-level officials have suggested plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

An independent energy policy expert, who was not involved with the research, described the report a “highly valuable addition” after a long period in which parts of the car industry argued there was too little information to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be made with extreme care and in the light of that data.”