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Plug-in hybrid electric vehicles produce nearly five times greater planet-heating pollution than lab-reported data show, as per a new analysis.

Widening Gap Between Official and Actual CO2 Output

Data shows that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy group. That differs significantly with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts studied data from in-vehicle energy use monitors of 800,000 cars sold in the EU between 2021 and 2023. The team discovered that real-world 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 increasing, while lab-reported figures are falling,” said a lead analyst involved in the report. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in electric power relative to overall mileage. They found that only 27% of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were significantly higher than official projections. That occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to combustion motors burning fossil fuels for nearly one-third of the travel completed in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output enabled four major carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend about €500 more per year in operating costs than is estimated under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large car industries.

Some high-level politicians have proposed plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An external energy economics expert, who was not involved with the study, called the report a “very useful contribution” after a long period in which segments of the car industry claimed there was insufficient information to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel cars,” they stated. “Any regulatory changes concerning PHEVs should be made with utmost caution and in the light of this evidence.”