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Plug-in hybrid cars emit nearly five times more planet-heating pollution than official figures show, according to a new report.

Widening Gap In Official and Actual CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a non-profit group. That contrasts significantly with lab tests, which assumed a 75% decrease in pollution.

Researchers studied information from in-vehicle energy use meters of 800,000 vehicles registered in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a senior analyst involved in the report. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric power relative to overall mileage. The team determined that just a quarter of travel was completed in EV mode, while official estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to function alone, resulting to engines using gasoline for nearly a third of the travel completed in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions enabled several major automaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra per year in operating costs than would be estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

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

Several senior officials have proposed plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One independent energy economics specialist, who was not involved with the research, described the report a “very useful contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they said. “All regulatory changes concerning PHEVs should be implemented with utmost caution and considering that evidence.”