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Plug-in hybrid electric vehicles release almost 5x more planet-heating emissions than official data show, according to a new analysis.

Growing Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than traditional gas and diesel cars, according to analysis conducted by a advocacy organization. That contrasts sharply with laboratory estimates, which assumed a 75% decrease in pollution.

Analysts examined information from onboard fuel consumption meters of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” said a lead researcher participating in the study. “That discrepancy is widening and creates a significant issue. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in battery mode relative to overall distance. They found that only 27% of driving was done in electric mode, whereas lab estimates suggested 84%.

Additionally, when running in electric mode, pollution amounts were well above lab projections. That happened because electric motors were insufficiently powerful sufficient to operate independently, leading to engines burning fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV CO2 output enabled several major carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 more annually in operating costs than would be assumed under lab conditions.

“The strong claims that automakers like to make about their PHEV cars are obviously way off the truth,” stated a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been drawn back into political debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large automotive industries.

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

An independent energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful contribution” after a long period in which segments of the automotive industry argued there was too little information to accurately assess real-world CO2 output.

“These findings show, without question, that the gap between official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert stated. “All policy changes regarding PHEVs should be implemented with extreme caution and considering that evidence.”