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Plug-in hybrid cars release almost 5x more planet-heating emissions than lab-reported data show, according to a new report.

Widening Gap In Official and Actual CO2 Output

Statistics reveals that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel cars, based on research conducted by a advocacy organization. That differs sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Analysts studied data from onboard energy use meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” stated a lead researcher participating in the study. “That gap is growing and poses a significant problem. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric mode relative to overall mileage. The team determined that just 27% of travel was completed in EV mode, while lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were well above official estimates. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to engines burning gasoline for nearly one-third of the travel covered in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four large automaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

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

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been drawn again into policy discussions as automakers have lobbied the EU to relax CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with significant automotive industries.

Several high-level officials have proposed PHEVs as a possible “flexibility” option to introduce in the legislation.

One external energy policy specialist, who was unaffiliated with the study, called the report a “very useful contribution” after years in which segments of the car industry claimed there was insufficient information to properly evaluate real-world emissions.

“The results show, without question, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert said. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and considering this data.”