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PHEVs produce almost five times greater planet-heating pollution than official data show, according to a recent report.

Growing Gap Between Official and Actual CO2 Output

Data reveals that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel cars, according to research carried out by a non-profit organization. This contrasts sharply with lab tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a senior analyst involved in the report. “That gap is widening and creates a serious issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in battery power compared to total distance. They found that only a quarter of travel was done in EV mode, whereas lab assumptions suggested 84%.

Additionally, when running in EV mode, pollution levels were significantly higher than lab projections. That occurred because electric motors were not strong sufficient to operate independently, leading to combustion motors burning fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV emissions allowed four large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 more annually in operating costs than would be estimated under lab tests.

“The strong statements that automakers often promote about their PHEV vehicles are obviously way off the truth,” stated a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been drawn back into policy discussions as carmakers have pressed the EU to relax CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with significant car industries.

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

An external energy policy expert, who was not involved with the research, described the analysis a “very useful contribution” after years in which parts of the automotive industry claimed there was too little data to accurately evaluate actual emissions.

“The results show, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional cars,” the expert said. “All regulatory changes regarding PHEVs should be made with extreme care and considering this evidence.”