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PHEVs produce almost five times greater planet-heating emissions than official figures show, according to a new report.

Widening Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit group. This contrasts significantly with lab tests, which assumed a three-quarters decrease in emissions.

Researchers examined information from onboard energy use meters of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” stated a lead researcher participating in the report. “This gap is widening and creates a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery power relative to total mileage. They determined that only 27% of driving was completed in electric mode, while lab estimates assumed over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than official estimates. This happened because electric motors were insufficiently powerful enough to function alone, resulting to engines burning gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output enabled four large automaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 more annually in running costs than would be assumed under laboratory tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the truth,” commented a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been brought again into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced intense pressure from the car sector and opposition from member states with large car manufacturing.

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

One independent energy economics specialist, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after years in which segments of the automotive industry claimed there was too little data to properly assess actual emissions.

“These findings show, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they stated. “All regulatory changes concerning PHEVs should be implemented with utmost care and considering that data.”