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Plug-in hybrid cars emit nearly 5x more planet-heating pollution than official data show, according to a recent analysis.

Growing Discrepancy In Lab and Actual CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit group. That differs sharply with lab tests, which suggested a three-quarters reduction in emissions.

Researchers examined data from onboard fuel consumption monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “This gap is growing and creates a serious issue. As a result, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Driving the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric mode relative to total distance. They found that just a quarter of travel was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in electric mode, emission levels were significantly higher than official estimates. This happened because EV motors were not strong enough to function alone, leading to engines burning gasoline for nearly one-third of the distance covered in EV mode.

Regulatory and Financial Implications

Based on calculations, the lowballing of PHEV emissions enabled four large automaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 extra per year in running costs than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been brought back into policy discussions as carmakers have pressed the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and resistance from member states with significant car manufacturing.

Some high-level officials have proposed PHEVs as a potential “flexibility” solution to introduce in the legislation.

An external energy policy specialist, who was not involved with the study, described the analysis a “highly valuable contribution” after years in which parts of the car sector argued there was too little information to properly assess real-world CO2 output.

“The results show, without question, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel cars,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with utmost caution and considering that evidence.”