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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating pollution than official data indicate, as per a new analysis.

Growing Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth less CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy group. This contrasts significantly with lab estimates, which suggested a 75% reduction in pollution.

Analysts studied information from in-vehicle energy use monitors of 800,000 cars sold in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” said a senior researcher involved in the report. “That discrepancy is widening and poses a significant problem. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Driving the Emissions Gap

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode compared to total distance. The team determined that only 27% of travel was completed in electric mode, while official estimates assumed 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than lab estimates. This occurred because EV motors were insufficiently powerful enough to function alone, leading to combustion motors burning fossil fuels for nearly a third of the travel completed in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

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

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly far from the truth,” stated a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought again into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and opposition from member states with significant car manufacturing.

Several high-level politicians have proposed PHEVs as a possible “flexibility” solution to introduce in the legislation.

An independent energy policy specialist, who was not involved with the study, called the report a “highly valuable addition” after a long period in which parts of the car sector claimed there was insufficient data to accurately assess actual emissions.

“The results show, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or conventional cars,” they stated. “All policy changes regarding PHEVs should be made with utmost care and considering this data.”