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Plug-in hybrid electric vehicles release almost 5x greater planet-heating emissions than official data indicate, as per a new report.

Widening Gap In Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit just 19% less CO₂ than traditional gas and diesel vehicles, according to research conducted by a non-profit group. This contrasts significantly with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers examined information from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” said a lead researcher participating in the report. “That discrepancy is widening and poses a serious issue. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power relative to total mileage. The team found that just 27% of travel was completed in electric mode, while lab estimates suggested 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than official estimates. This happened because electric motors were not strong enough to function independently, resulting to engines burning gasoline for almost a third of the travel completed in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV CO2 output enabled four major automaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 extra per year in operating costs than is estimated under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn back into policy discussions as carmakers have pressed the EU to relax CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with significant car manufacturing.

Several senior officials have proposed plug-in hybrids as a potential “compromise” option to introduce in the regulation.

An external energy economics specialist, who was not involved with the study, described the analysis a “very useful contribution” after years in which parts of the automotive sector claimed there was insufficient information to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of that data.”