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Plug-in hybrid cars release nearly five times more planet-heating emissions than lab-reported data show, according to a new report.

Widening Gap In Official and Actual Emissions

Data shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit organization. This contrasts sharply with laboratory tests, which assumed a 75% decrease in pollution.

Researchers studied data from in-vehicle energy use meters of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” stated a lead analyst involved in the report. “This discrepancy is growing and poses a serious problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in battery power relative to overall mileage. The team found that only a quarter of driving was completed in EV mode, while lab assumptions suggested 84%.

Additionally, when running in EV mode, pollution levels were well above official projections. This occurred because electric motors were not strong sufficient to operate alone, leading to engines using gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV emissions enabled several large automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 extra annually in running costs than would be estimated under laboratory tests.

“The bold statements that manufacturers like to make about their PHEV cars are clearly way off the truth,” commented a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into political discussions as automakers have lobbied the European Union to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and opposition from EU countries with significant car manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” option to include in the legislation.

An external energy economics specialist, who was not involved with the research, called the report a “very useful addition” after a long period in which segments of the automotive sector argued there was insufficient information to properly evaluate real-world emissions.

“These findings show, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” they stated. “Any regulatory changes concerning PHEVs should be made with utmost caution and considering that data.”