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Plug-in hybrid cars emit nearly 5x greater global warming pollution than lab-reported figures show, according to a new report.

Widening Discrepancy Between Official and Actual Emissions

Data shows that PHEVs emit only 19% less CO₂ than conventional gas and diesel cars, based on research conducted by a non-profit group. This differs sharply with laboratory tests, which assumed a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 cars sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” stated a lead analyst participating in the report. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode compared to overall distance. The team determined that only 27% of travel was done in electric mode, whereas official assumptions suggested 84%.

Additionally, when running in EV mode, emission amounts were well above lab estimates. That happened because EV motors were not strong enough to function independently, resulting to engines using fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output enabled four major automaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

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

“The strong claims that automakers like to make about their PHEV cars are obviously way off the truth,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little improved than regular gas and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have lately been brought back into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine cars in 2035 has faced intense pressure from the car sector and opposition from EU countries with large car industries.

Several senior officials have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

One independent energy economics expert, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which parts of the car sector argued there was insufficient information to properly evaluate actual CO2 output.

“The results show, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel vehicles,” they stated. “All regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of this evidence.”