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Plug-in hybrid cars emit nearly 5x more global warming emissions than official data show, according to a recent analysis.

Widening Discrepancy Between Lab and Actual Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel cars, based on analysis carried out by a advocacy group. This contrasts sharply with lab tests, which assumed a 75% reduction in emissions.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a lead researcher involved in the study. “This discrepancy is growing and poses a significant problem. As a result, PHEVs emit almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode relative to total distance. They determined that only 27% of travel was completed in EV mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were well above official projections. That happened because electric motors were not strong enough to function independently, resulting to engines using fossil fuels for nearly one-third of the travel completed in EV mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions enabled several major carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in running costs than is assumed under laboratory tests.

“The strong statements that manufacturers like to make about their PHEV vehicles are clearly way off the mark,” commented a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been brought back into political debates as automakers have lobbied the EU to relax CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with large automotive manufacturing.

Several senior politicians have proposed PHEVs as a potential “flexibility” option to introduce in the regulation.

An independent energy economics expert, who was unaffiliated with the study, called the report a “very useful addition” after years in which parts of the car sector argued there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” they said. “Any policy changes concerning PHEVs should be made with extreme care and considering that data.”