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Plug-in hybrid electric vehicles produce almost five times more planet-heating pollution than official data indicate, according to a recent analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel vehicles, according to research conducted by a non-profit organization. This contrasts significantly with lab tests, which assumed a three-quarters decrease in pollution.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” said a senior analyst involved in the study. “This discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric mode compared to overall mileage. They found that just 27% of travel was completed in EV mode, while lab estimates suggested 84%.

Even, when operating in EV mode, emission levels were well above official projections. That occurred because EV motors were not strong enough to function alone, resulting to engines burning fossil fuels for nearly one-third of the travel completed in EV mode.

Policy and Financial Implications

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

Additionally, drivers of PHEVs would spend about €500 more annually in running costs than is estimated under laboratory tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the truth,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into political discussions as automakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large car manufacturing.

Several high-level officials have suggested PHEVs as a potential “compromise” solution to introduce in the regulation.

An independent energy economics specialist, who was not involved with the study, called the analysis a “very useful contribution” after years in which parts of the automotive sector claimed there was too little information to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they stated. “All policy changes regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”