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Plug-in hybrid electric vehicles release almost five times more planet-heating emissions than official data show, according to a new report.

Growing Gap In Official and Real-World Emissions

Data shows that PHEVs emit only 19% less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a advocacy group. This differs significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Analysts studied information from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a lead researcher involved in the study. “That discrepancy is widening and poses a significant problem. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of miles driven in battery mode relative to overall mileage. They determined that just 27% of driving was done in electric mode, while official assumptions assumed over four-fifths.

Additionally, when operating in EV mode, emission amounts were significantly higher than official projections. This happened because electric motors were not strong enough to operate independently, leading to engines burning gasoline for almost a third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV emissions enabled four large automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra per year in operating costs than is assumed under lab conditions.

“The strong statements that automakers like to make about their PHEV cars are obviously way off the truth,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy debates as carmakers have pressed the EU to relax CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant car manufacturing.

Several senior officials have suggested plug-in hybrids as a possible “compromise” solution to include in the legislation.

An external energy economics expert, who was unaffiliated with the study, called the report a “very useful addition” after years in which parts of the automotive industry claimed there was too little data to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional vehicles,” they stated. “Any regulatory changes regarding PHEVs should be implemented with utmost care and considering this data.”