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Plug-in hybrid electric vehicles produce almost 5x more planet-heating emissions than lab-reported data indicate, as per a new report.

Widening Gap In Lab and Real-World Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, according to research carried out by a advocacy organization. This differs significantly with laboratory tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use monitors of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” stated a lead analyst participating in the report. “This gap is widening and poses a serious issue. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of miles travelled in electric power relative to overall distance. The team found that just 27% of travel was done in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, emission levels were significantly higher than lab estimates. That happened because electric motors were not strong enough to function alone, resulting to combustion motors using fossil fuels for nearly a third of the travel completed in electric mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed four large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

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

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into political debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant automotive manufacturing.

Several high-level politicians have suggested PHEVs as a possible “compromise” option to introduce in the regulation.

An external energy economics expert, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the automotive industry argued there was insufficient information to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel cars,” they stated. “Any regulatory changes regarding PHEVs should be made with utmost care and in the light of this evidence.”