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PHEVs release nearly 5x greater global warming emissions than lab-reported data show, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a non-profit group. This differs sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Analysts examined information from in-vehicle energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a senior researcher involved in the study. “That gap is growing and creates a significant problem. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in battery power relative to total mileage. The team determined that just 27% of driving was done in EV mode, while official estimates suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than official estimates. That occurred because electric motors were insufficiently powerful sufficient to operate independently, leading to combustion motors burning fossil fuels for nearly one-third of the distance completed in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several large automaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more annually in running expenses than is assumed under lab tests.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have recently been brought back into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with significant automotive manufacturing.

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

One independent energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the car industry claimed there was too little data to properly evaluate actual emissions.

“These findings demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” they stated. “All regulatory adjustments regarding PHEVs should be implemented with extreme caution and in the light of that data.”