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Plug-in hybrid electric vehicles emit almost 5x greater global warming pollution than lab-reported figures show, according to a new analysis.

Growing Gap In Official and Actual CO2 Output

Data reveals that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit group. That differs significantly with lab estimates, which suggested a 75% reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” stated a senior researcher participating in the report. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs pollute nearly as much as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to overall mileage. The team found that just 27% of travel was done in electric mode, while official estimates suggested 84%.

Additionally, when running in electric mode, pollution amounts were well above lab estimates. This occurred because electric motors were insufficiently powerful enough to operate independently, leading to engines using gasoline for nearly a third of the distance covered in electric mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions enabled several large carmaker groups to escape over €5bn in fines between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 extra annually in operating expenses than is estimated under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought back into political debates as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and opposition from member states with large automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One independent energy economics specialist, who was not involved with the study, called the report a “highly valuable addition” after a long period in which parts of the car industry claimed there was too little information to properly assess actual emissions.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and in the light of that data.”