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Plug-in hybrid electric vehicles release nearly 5x more planet-heating emissions than official figures indicate, as per a new analysis.

Widening Gap In Official and Actual CO2 Output

Data shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, based on research carried out by a advocacy group. That differs sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Researchers examined information from onboard energy use monitors of eight hundred thousand cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a senior researcher participating in the study. “This discrepancy is widening and poses a significant problem. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode compared to total distance. They determined that only a quarter of travel was completed in electric mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, pollution amounts were well above lab estimates. That occurred because EV motors were not strong sufficient to function independently, leading to combustion motors burning fossil fuels for almost one-third of the travel completed in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed four large automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in operating costs than is estimated under laboratory conditions.

“The bold statements that manufacturers often promote about their PHEV cars are obviously way off the truth,” stated a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Hybrid cars have lately been brought again into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from member states with large car industries.

Some high-level politicians have suggested plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

One independent energy policy expert, who was not involved with the study, described the analysis a “highly valuable addition” after a long period in which parts of the automotive industry claimed there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the gap in official and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert stated. “Any regulatory adjustments concerning PHEVs should be made with utmost care and considering this evidence.”