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Plug-in hybrid cars release almost 5x greater planet-heating emissions than lab-reported data indicate, according to a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit group. That differs sharply with lab estimates, which assumed a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” said a lead analyst participating in the report. “That gap is growing and poses a significant problem. Consequently, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to total distance. The team determined that just a quarter of driving was completed in EV mode, whereas official assumptions suggested 84%.

Even, when operating in electric mode, pollution levels were well above lab projections. This occurred because electric motors were not strong sufficient to function independently, resulting to combustion motors using fossil fuels for nearly a third of the travel completed in electric mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV emissions enabled several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 extra per year in running expenses than would be assumed under lab tests.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn back into policy discussions as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large car manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

An external energy economics specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the automotive sector claimed there was too little data to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert said. “All regulatory changes concerning PHEVs should be implemented with extreme caution and in the light of this data.”