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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating emissions than official data show, according to a recent analysis.

Widening Gap Between Lab and Actual CO2 Output

Data reveals that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit organization. That contrasts significantly with laboratory tests, which suggested a 75% reduction in pollution.

Analysts studied information from onboard energy use meters of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a lead researcher involved in the report. “That discrepancy is widening and creates a significant problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in battery mode relative to total mileage. They determined that only 27% of travel was done in EV mode, while official assumptions assumed 84%.

Even, when operating in EV mode, emission levels were well above lab estimates. That occurred because electric motors were not strong enough to operate alone, leading to combustion motors using fossil fuels for nearly one-third of the distance completed in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed several large automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra annually in operating expenses than is assumed under laboratory tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” stated a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have lately been brought again into policy discussions as carmakers have pressed the EU to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car industries.

Several high-level officials have suggested plug-in hybrids as a possible “flexibility” option to include in the regulation.

One independent energy economics expert, who was not involved with the study, described the analysis a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little data to accurately assess real-world emissions.

“These findings demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” they said. “All policy changes regarding PHEVs should be made with utmost caution and in the light of this data.”