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Plug-in hybrid electric vehicles emit almost 5x greater global warming emissions than official figures indicate, as per a new report.

Widening Discrepancy Between Official and Actual CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research carried out by a non-profit organization. That differs significantly with laboratory tests, which suggested a 75% reduction in emissions.

Analysts studied information from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” said a senior analyst involved in the report. “That discrepancy is widening and poses a significant issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in battery power compared to overall mileage. The team found that only a quarter of travel was done in EV mode, whereas lab assumptions assumed 84%.

Additionally, when running in EV mode, emission amounts were well above lab projections. This happened because electric motors were insufficiently powerful enough to operate independently, leading to engines burning gasoline for almost a third of the distance covered in electric mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four large automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

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

“The bold statements that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn back into political discussions as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant car manufacturing.

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

One independent energy policy specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which segments of the car sector claimed there was too little information to accurately assess real-world CO2 output.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel vehicles,” they stated. “All policy changes regarding PHEVs should be made with extreme care and in the light of that evidence.”