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PHEVs produce almost 5x greater planet-heating emissions than official figures show, according to a new report.

Widening Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a non-profit group. This contrasts sharply with lab estimates, which suggested a 75% decrease in pollution.

Researchers examined data from onboard fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. The team found 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 increasing, while lab-reported figures are decreasing,” said a senior researcher involved in the study. “This discrepancy is widening and creates a significant issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles travelled in battery mode relative to overall mileage. The team determined that only 27% of driving was done in EV mode, whereas lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than official estimates. That happened because EV motors were insufficiently powerful sufficient to function independently, resulting to engines using gasoline for nearly a third of the distance covered in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions allowed four large carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra annually in operating expenses than would be assumed under laboratory tests.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are clearly far from the truth,” stated a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been brought back into policy discussions as automakers have pressed the European Union to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and resistance from member states with large car industries.

Some senior officials have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

An external energy policy expert, who was unaffiliated with the study, called the report a “highly valuable addition” after years in which parts of the automotive industry argued there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or diesel cars,” the expert said. “All policy changes regarding PHEVs should be made with utmost care and considering this evidence.”