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Plug-in hybrid cars release almost 5x greater planet-heating emissions than official figures show, as per a new analysis.

Growing Discrepancy In Lab and Real-World Emissions

Data reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a advocacy organization. This differs significantly with laboratory tests, which assumed a 75% decrease in emissions.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a senior researcher involved in the report. “That discrepancy is widening and poses a serious problem. As a result, PHEVs pollute nearly as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery power compared to total mileage. They found that just a quarter of driving was done in electric mode, whereas lab estimates assumed 84%.

Additionally, when running in EV mode, pollution levels were well above lab projections. That occurred because electric motors were not strong enough to operate alone, resulting to engines burning gasoline for almost a third of the distance completed in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV CO2 output enabled four major automaker groups to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 extra per year in operating expenses than would be assumed under laboratory tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been brought again into policy discussions as automakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant automotive manufacturing.

Several high-level politicians have suggested plug-in hybrids as a potential “compromise” option to introduce in the legislation.

One external energy economics expert, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry argued there was too little data to accurately evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they said. “All regulatory changes regarding PHEVs should be made with utmost caution and considering this data.”