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Plug-in hybrid electric vehicles emit almost 5x more global warming emissions than lab-reported figures show, according to a recent analysis.

Growing Gap Between Official and Actual Emissions

Statistics reveals that PHEVs emit just 19% less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This differs sharply with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers studied data from in-vehicle energy use monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a senior researcher participating in the report. “This gap is growing and poses a serious problem. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode compared to total distance. The team determined that only 27% of travel was done in EV mode, while official estimates suggested over four-fifths.

Even, when running in electric mode, pollution levels were well above official estimates. That occurred because electric motors were insufficiently powerful enough to function alone, resulting to engines burning fossil fuels for nearly one-third of the travel completed in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled four large carmaker groups to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

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

“The strong statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the mark,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been brought again into policy discussions as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from EU countries with large automotive manufacturing.

Some high-level politicians have suggested plug-in hybrids as a potential “compromise” option to introduce in the legislation.

An external energy policy specialist, who was not involved with the study, described the report a “very useful contribution” after years in which segments of the car sector argued there was insufficient data to properly assess actual emissions.

“These findings show, without question, that the difference in official and actual PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” they stated. “Any policy adjustments regarding PHEVs should be made with extreme caution and in the light of that data.”