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Plug-in hybrid cars produce almost 5x greater planet-heating emissions than official data indicate, according to a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy organization. This differs sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use meters of 800,000 vehicles registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior analyst involved in the study. “This discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total mileage. The team determined that only 27% of travel was completed in electric mode, while official estimates assumed 84%.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. This happened because EV motors were not strong enough to function alone, leading to combustion motors using gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 more per year in operating expenses than is estimated under laboratory tests.

“The bold statements that manufacturers like to make about their PHEV cars are clearly far from the truth,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Industry Pressure

Hybrid cars have lately been brought back into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “compromise” option to include in the legislation.

An external energy policy specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after a long period in which parts of the automotive industry argued there was insufficient data to properly evaluate actual CO2 output.

“The results demonstrate, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional cars,” the expert said. “All policy adjustments concerning PHEVs should be implemented with extreme caution and considering this evidence.”