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Plug-in hybrid cars produce nearly 5x greater planet-heating emissions than official figures show, as per a recent analysis.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit organization. That contrasts significantly with lab estimates, which suggested a 75% decrease in emissions.

Researchers examined data from in-vehicle energy use meters of 800,000 cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a lead analyst participating in the report. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to total distance. They found that just 27% of driving was completed in EV mode, whereas official assumptions assumed over four-fifths.

Even, when running in electric mode, pollution levels were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful enough to function independently, leading to combustion motors burning fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled several large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend about €500 more annually in running costs than would be estimated under lab tests.

“The bold statements that manufacturers like to make about their PHEV cars are obviously way off the mark,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Policy Discussion and Automotive Lobbying

Hybrid cars have lately been drawn back into policy discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with significant car industries.

Some high-level officials have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

An external energy policy specialist, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the automotive sector claimed there was too little information to properly evaluate actual emissions.

“These findings show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” the expert said. “All regulatory changes regarding PHEVs should be implemented with utmost caution and considering this data.”