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Plug-in hybrid cars emit almost 5x more planet-heating emissions than official figures indicate, according to a new analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel cars, according to analysis carried out by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a 75% reduction in emissions.

Analysts examined data from in-vehicle energy use meters of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a senior researcher involved in the report. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode relative to total distance. They found that only a quarter of travel was completed in EV mode, whereas lab assumptions assumed 84%.

Even, when running in EV mode, pollution levels were significantly higher than official estimates. That occurred because EV motors were insufficiently powerful sufficient to function independently, resulting to combustion motors using gasoline for nearly a third of the travel completed in electric mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 more per year in running expenses than is estimated under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” commented a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy debates as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car industry and opposition from member states with significant automotive manufacturing.

Some senior officials have suggested PHEVs as a potential “compromise” solution to include in the regulation.

One independent energy economics expert, who was not involved with the study, described the analysis a “very useful contribution” after a long period in which segments of the car sector argued there was too little information to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with extreme caution and considering this data.”