Study Reveals PHEVs Consume Triple the Fuel Than Previously Estimated

In a significant revelation, the largest real-world study to date on plug-in hybrid vehicles (PHEVs) suggests that these vehicles consume much more gasoline than previously reported. This comes at a time when Europe is reconsidering PHEV regulations, with industry stakeholders pushing to retain existing, albeit inaccurate, metrics.

Understanding the landscape of electric vehicles can be quite complex, with various types such as BEVs, FCEVs, EREVs, and PHEVs. At Electrek, the focus is often on battery electric vehicles, or what many refer to as “all-electric” vehicles. However, another category that garners attention is plug-in hybrids, which blend internal combustion and electric powertrains.

PHEVs present an alternative to conventional hybrids by drawing energy both from gasoline and the electric grid. This duality allows for the potential use of cleaner energy sources like solar or wind power. Automakers favor PHEVs as they continue to sell combustion engines, a technology they have refined over decades. Despite their potential for reduced emissions, PHEVs often fail to meet these expectations.

Previous research, including several studies before, indicates that PHEVs use more gasoline and emit more pollutants than advertised. Often, these vehicles are not plugged in as frequently as necessary, leading them to function similarly to conventional hybrids.

Study Reveals Higher Fuel Consumption in PHEVs

The recent study conducted by the Fraunhofer Institute utilized data from 981,035 PHEVs across Europe. The findings reveal that these vehicles consume over three times the fuel than the estimates provided by the EU’s PHEV regulations. These vehicles, expected to consume 1.57 liters per 100 kilometers, actually used an average of 6.12 liters.

Further analysis shows that in “charge depleting” mode, where the battery depletes rather than being sustained by the engine, PHEVs still use more fuel than anticipated. The average fuel consumption in this mode was 2.98 liters per 100 kilometers, significantly higher than the estimated 1.57 liters.

The study also examined charging habits across different brands, finding that luxury brands like Porsche, Bentley, and Ferrari were among the least charged vehicles. Interestingly, the study highlighted that the average Porsche was charged for only 7kWh over a distance of 27,000 kilometers, with a median usage of 0% electric power.

Addressing the Discrepancy

While WLTP estimates for conventional vehicles are often about 20% off, the over 300% discrepancy for PHEVs presents a significant challenge. The EU is aware of this issue and plans to adjust the “utility factor” in 2025, which estimates the usage of fossil versus electric power in PHEVs. However, there is concern over lobbying efforts to maintain the current utility factor, which could hinder progress.

To bridge the gap between estimates and real-world data, the study suggests adopting measures like “display transparency” to inform drivers of their fuel usage and “inducement” to encourage regular charging. Nonetheless, the most impactful solution would be to ensure that utility factor adjustments are not compromised.

The study warns that if utility factor changes are rolled back, an additional 23-25 million tons of CO2 could be emitted over the next 20 years. It advocates for strengthening these adjustments in 2027 to align more closely with the empirical data gathered from nearly a million vehicles.

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