Fuel consumption of 'plug-in' hybrids: The truth behind the numbers

Hybrid Gas Guzzlers "Plug-in" Hybrids Consume Much More Than Stated

2026-02-23 Source: dpa 1 min Reading Time

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Paper is patient, even when it comes to numbers. As a Fraunhofer study now shows, the fuel consumption figures for "plug-in" hybrids differ significantly from the truth ...

Anyone relying on the fuel consumption figures in the description of their "plug-in" hybrid might be in for a surprise. Researchers have found in real-world tests that theory and practice differ significantly ...(Image: Koenigsreuther) — Anyone relying on the fuel consumption figures in the description of their "plug-in" hybrid might be in for a surprise. Researchers have found in real-world tests that theory and practice differ significantly ...
(Image: Koenigsreuther)

In everyday operation, "plug-in" hybrids are apparently much thirstier than the figures on paper admit. On average, they consume about four times the official value! This was revealed by a study conducted by the Fraunhofer Institute for Systems and Innovation Research (ISI) and other organizations. The results are based on real-world data collected from nearly one million vehicles of various manufacturers, covering model years 2021 to 2023. While it is known that the technical consumption figures for vehicles of all types do not reflect actual driving practice, the discrepancy for "plug-in" hybrids is extreme. While the average standard consumption was approximately 0.4 gallons per 62 miles, the real-world data showed around 1.6 gallons per 62 miles. Accordingly, CO₂ emissions and fuel costs are significantly higher, as the researchers note.

Shock! Even Purely Electric More Fuel than Expected

According to the report, the discrepancy is partly due to the fact that, even in predominantly electric discharge mode, the cars consumed an average of about 78 miles per gallon in everyday use, which is much higher than previously thought. This was a shock for all the scientists involved, as commented by Patrick Plötz, the study leader from ISI. Based on the new findings, the scientists are therefore calling for EU regulations to be adjusted. The gap between theoretical and actual fuel consumption must be significantly reduced through stricter guidelines for calculating the fuel consumption of "plug-in" hybrids. Such an adjustment would also have implications for car manufacturers, as compliance with the EU-mandated CO₂ fleet values is calculated based on WLTP consumption figures. The WLTP specifies a precise sequence of speeds and accelerations, aiming to determine comparable consumption values. However, for newer "plug-in" hybrids, the difference might be smaller, as the rules for measuring consumption have already been tightened.

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