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Plug-in hybrid electric vehicles produce nearly 5x more global warming emissions than official data show, according to a new analysis.

Widening Discrepancy Between Official and Actual Emissions

Data shows that PHEVs emit only 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. That differs sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers examined information from onboard fuel consumption meters of 800,000 vehicles sold in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” stated a senior analyst participating in the report. “That discrepancy is growing and poses a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in electric power compared to overall mileage. The team determined that just a quarter of travel was done in electric mode, whereas official assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful enough to function independently, leading to engines burning gasoline for nearly one-third of the travel completed in electric mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV CO2 output enabled four large automaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could pay about €500 extra annually in operating costs than is assumed under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and saving money. In reality, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn back into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with large car manufacturing.

Some high-level politicians have suggested plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

One independent energy policy expert, who was not involved with the research, called the report a “highly valuable contribution” after years in which segments of the automotive sector argued there was insufficient information to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is significantly larger than for petrol or conventional vehicles,” they stated. “All regulatory changes regarding PHEVs should be implemented with utmost care and in the light of that evidence.”