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Plug-in hybrid electric vehicles release nearly five times greater global warming pollution than lab-reported figures show, according to a new report.

Growing Discrepancy In Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy organization. This differs significantly with laboratory tests, which suggested a 75% decrease in emissions.

Researchers studied information from onboard energy use monitors of 800,000 cars registered in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” said a senior analyst participating in the study. “This gap is widening and creates a significant issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in battery power compared to total mileage. They found that only a quarter of travel was done in electric mode, while official assumptions suggested 84%.

Even, when operating in electric mode, emission levels were significantly higher than lab projections. This occurred because electric motors were not strong sufficient to operate alone, leading to combustion motors using fossil fuels for almost one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

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

Additionally, owners of PHEVs would spend about €500 more annually in running costs than would be assumed under lab conditions.

“The bold claims that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

Hybrid cars have recently been brought again into political discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the automotive sector and opposition from member states with large car industries.

Several high-level politicians have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

An external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry argued there was too little data to accurately evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they stated. “Any policy changes concerning PHEVs should be made with utmost caution and considering that evidence.”