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Plug-in hybrid cars produce nearly five times more planet-heating emissions than official data indicate, according to a new report.

Growing Gap In Official and Real-World Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a advocacy organization. This contrasts significantly with lab tests, which suggested a 75% reduction in pollution.

Researchers examined information from onboard energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a senior analyst participating in the study. “That gap is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to total distance. They determined that just 27% of travel was done in EV mode, while official assumptions assumed over four-fifths.

Even, when running in EV mode, emission amounts were significantly higher than lab projections. This occurred because electric motors were not strong sufficient to operate independently, resulting to combustion motors using gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 extra annually in running expenses than is assumed under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into political discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from member states with significant car industries.

Several high-level politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive industry argued there was too little data to properly assess real-world CO2 output.

“The results demonstrate, without question, that the difference between lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and considering this data.”