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PHEVs emit nearly five times greater global warming pollution than lab-reported data show, according to a recent report.

Widening Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a advocacy group. That differs significantly with lab tests, which assumed a 75% reduction in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a lead researcher involved in the report. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute almost as heavily as petrol cars.”

Key Factors Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric mode compared to total mileage. They determined that only 27% of driving was done in EV mode, while official estimates suggested 84%.

Even, when running in electric mode, emission levels were well above official estimates. This happened because electric motors were not strong enough to operate independently, resulting to engines using fossil fuels for nearly one-third of the distance completed in EV mode.

Policy and Financial Consequences

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

Additionally, drivers of PHEVs could pay approximately €500 extra per year in running expenses than is assumed under lab conditions.

“The strong claims that manufacturers often promote about their PHEV cars are clearly way off the truth,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid cars have recently been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with large car industries.

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

One independent energy policy expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after a long period in which segments of the automotive industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional cars,” the expert stated. “All regulatory changes regarding PHEVs should be made with utmost caution and considering this evidence.”