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Plug-in hybrid cars emit almost 5x more planet-heating pollution than official figures indicate, according to a recent analysis.

Growing Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy organization. This contrasts sharply with laboratory tests, which assumed a 75% decrease in pollution.

Analysts examined information from onboard fuel consumption monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” said a senior researcher participating in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric power relative to overall mileage. The team determined that only a quarter of travel was done in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than official estimates. That happened because electric motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for almost a third of the travel completed in electric mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled four large automaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 extra annually in operating expenses than would be estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV vehicles are obviously way off the truth,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into political debates as automakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car industry and opposition from EU countries with large automotive industries.

Several high-level politicians have suggested PHEVs as a possible “flexibility” solution to introduce in the legislation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the automotive sector argued there was insufficient data to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ output is significantly larger than for petrol or diesel vehicles,” they said. “All regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of this data.”