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Plug-in hybrid cars produce almost five times greater planet-heating emissions than official figures show, as per a new analysis.

Widening Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit group. That contrasts significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Analysts examined information from onboard energy use monitors 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 higher than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” said a senior analyst participating in the study. “That discrepancy is widening and poses a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power compared to total mileage. The team found that just a quarter of driving was done in EV mode, whereas official estimates assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than lab estimates. That occurred because electric motors were insufficiently powerful enough to function independently, resulting to engines using gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions allowed four large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more annually in operating expenses than would be estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their PHEV cars are clearly far from the mark,” stated a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have lately been brought back into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced intense pressure from the car industry and opposition from member states with large automotive manufacturing.

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

An external energy economics specialist, who was not involved with the research, described the analysis a “very useful addition” after years in which parts of the car sector argued there was too little data to accurately assess real-world emissions.

“The results show, without question, that the difference in lab and actual PHEV energy use and CO₂ output is significantly greater than for petrol or diesel cars,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with extreme care and in the light of that evidence.”