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PHEVs produce almost 5x more planet-heating pollution than official data indicate, as per a new report.

Growing Gap In Lab and Real-World CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit group. This contrasts sharply with lab estimates, which assumed a 75% reduction in emissions.

Analysts studied information from onboard energy use monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a lead researcher involved in the study. “This discrepancy is growing and poses a serious problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric mode relative to total distance. The team found that only a quarter of driving was completed in EV mode, while lab estimates assumed 84%.

Even, when operating in EV mode, pollution amounts were significantly higher than lab projections. This occurred because electric motors were not strong enough to function alone, leading to combustion motors using gasoline for almost one-third of the travel covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output enabled four large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 extra per year in operating costs than would be assumed under laboratory conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into policy discussions as automakers have lobbied the EU to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large car manufacturing.

Some senior politicians have suggested PHEVs as a possible “compromise” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the study, called the report a “very useful addition” after years in which parts of the car sector claimed there was insufficient information to accurately evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel cars,” they stated. “Any policy changes regarding PHEVs should be implemented with extreme caution and considering this data.”