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Plug-in hybrid cars produce almost five times more planet-heating pollution than lab-reported data indicate, according to a new report.

Widening Gap In Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel cars, based on research carried out by a advocacy organization. That differs significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a lead researcher participating in the report. “That gap is widening and poses a serious problem. As a result, PHEVs pollute almost as much as petrol cars.”

Primary Factors Behind the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the percentage of miles driven in electric power relative to overall distance. They determined that only 27% of travel was done in electric mode, while official estimates suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were well above official estimates. This occurred because EV motors were not strong enough to function independently, resulting to engines using fossil fuels for nearly one-third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled four major automaker groups to escape over €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in running expenses than would be estimated under laboratory conditions.

“The bold claims that automakers like to make about their PHEV vehicles are obviously way off the truth,” stated a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into political discussions as carmakers have pressed the European Union to relax CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant automotive manufacturing.

Some high-level officials have suggested plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One external energy policy expert, who was unaffiliated with the study, called the report a “very useful addition” after a long period in which parts of the automotive industry argued there was too little data to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional cars,” they said. “Any regulatory changes regarding PHEVs should be made with utmost care and in the light of that data.”