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PHEVs release almost 5x more planet-heating pollution than lab-reported data indicate, according to a recent report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. This contrasts significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers studied data from onboard energy use monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” said a senior analyst participating in the report. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery mode compared to total distance. The team determined that just 27% of travel was completed in electric mode, whereas lab assumptions assumed 84%.

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

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled four major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more per year in running expenses than would be estimated under laboratory tests.

“The strong statements that automakers often promote about their PHEV vehicles are clearly far from the mark,” commented a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into political discussions as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and opposition from member states with significant automotive manufacturing.

Several high-level officials have proposed PHEVs as a possible “flexibility” option to include in the regulation.

An external energy economics expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was too little information to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel cars,” they said. “Any policy changes regarding PHEVs should be made with extreme caution and considering that data.”