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Plug-in hybrid cars release nearly 5x more global warming pollution than lab-reported figures indicate, according to a new report.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, based on research carried out by a non-profit group. That contrasts sharply with laboratory tests, which assumed a three-quarters decrease in pollution.

Analysts examined data from in-vehicle energy use meters of eight hundred thousand cars registered in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” stated a lead researcher involved in the study. “This discrepancy is widening and poses a significant issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “utility factor” – the percentage of miles travelled in electric mode relative to overall mileage. They found that just a quarter of driving was completed in electric mode, while lab estimates assumed over four-fifths.

Even, when operating in electric mode, emission amounts were well above official estimates. This occurred because EV motors were insufficiently powerful sufficient to function independently, resulting to engines burning fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output enabled several large automaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 more annually in running costs than is estimated under laboratory conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Discussion and Industry Pressure

Hybrid cars have recently been drawn again into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from member states with significant automotive manufacturing.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

One external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little information to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” the expert stated. “All regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of this data.”