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Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than lab-reported figures show, according to a recent report.

Growing Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release just 19% lower CO₂ than traditional petrol and diesel vehicles, according to research carried out by a advocacy organization. That contrasts significantly with laboratory tests, which suggested a three-quarters reduction in emissions.

Analysts examined data from onboard fuel consumption meters of 800,000 vehicles sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a lead analyst participating in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to overall distance. They determined that only a quarter of travel was completed in electric mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were well above lab projections. This occurred because EV motors were insufficiently powerful sufficient to function independently, resulting to engines burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed four large automaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 more annually in operating costs than would be estimated under laboratory tests.

“The bold claims that automakers often promote about their PHEV cars are obviously way off the mark,” stated a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Hybrid cars have recently been brought back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large automotive industries.

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

An external energy policy specialist, who was not involved with the research, described the report a “very useful addition” after years in which segments of the car industry argued there was too little data to properly evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” they said. “Any regulatory changes concerning PHEVs should be implemented with extreme care and in the light of this evidence.”