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Plug-in hybrid cars produce nearly five times greater planet-heating emissions than lab-reported figures show, according to a new analysis.

Widening Gap Between Lab and Actual CO2 Output

Data reveals that PHEVs emit just 19% lower CO₂ than traditional gas and diesel cars, according to analysis carried out by a non-profit organization. This contrasts significantly with lab tests, which suggested a 75% decrease in emissions.

Analysts studied information from onboard fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world 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 lab-reported figures are decreasing,” said a lead researcher participating in the study. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total distance. They found that only a quarter of driving was completed in electric mode, whereas lab assumptions suggested 84%.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. That happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors burning gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV emissions enabled several major automaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more per year in operating costs than is estimated under lab conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the mark,” commented a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Automotive Lobbying

Hybrid vehicles have lately been drawn back into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with large automotive industries.

Several high-level politicians have proposed PHEVs as a possible “flexibility” solution to introduce in the regulation.

One external energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after years in which segments of the car industry argued there was too little information to properly assess actual CO2 output.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” they said. “All regulatory adjustments regarding PHEVs should be implemented with extreme care and considering this evidence.”