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Plug-in hybrid electric vehicles produce almost five times more planet-heating emissions than official figures indicate, according to a new report.

Widening Discrepancy In Lab and Actual Emissions

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit organization. That differs significantly with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers examined information from onboard energy use meters of eight hundred thousand cars registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” stated a senior analyst involved in the report. “That discrepancy is widening and creates a serious problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power compared to overall mileage. They found that just a quarter of travel was done in EV mode, while lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were well above official estimates. That occurred because EV motors were insufficiently powerful enough to function independently, resulting to engines using fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled four large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 extra per year in running costs than is assumed under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid cars are obviously way off the mark,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little improved than regular gas and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into political debates as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car sector and opposition from EU countries with large car manufacturing.

Several senior officials have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

An independent energy policy expert, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which parts of the car industry claimed there was too little data to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert stated. “Any regulatory adjustments concerning PHEVs should be made with extreme care and in the light of this data.”