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Plug-in hybrid cars release nearly five times more global warming pollution than official figures show, according to a new analysis.

Growing Discrepancy In Official and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy organization. This contrasts significantly with lab tests, which assumed a 75% decrease in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Actual emissions are rising, while official emissions are falling,” stated a senior analyst participating in the study. “That discrepancy is widening and creates a serious problem. As a result, PHEVs emit almost as much as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in battery mode relative to overall distance. They determined that just 27% of driving was done in electric mode, while lab estimates assumed 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than official estimates. That happened because electric motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors using gasoline for nearly one-third of the travel covered in EV mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed four large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 more annually in operating costs than would be estimated under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Policy Debate and Automotive Lobbying

Hybrid cars have recently been drawn back into policy debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with large automotive industries.

Several senior officials have proposed PHEVs as a potential “compromise” solution to introduce in the regulation.

An independent energy economics expert, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the car sector claimed there was too little information to properly evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with extreme care and in the light of that data.”