Environmental Impact of Plug-in Hybrid Vehicles - The End of the PHEV Myth: In Real-World Driving, They Were "Almost Gasoline Cars"

Environmental Impact of Plug-in Hybrid Vehicles - The End of the PHEV Myth: In Real-World Driving, They Were "Almost Gasoline Cars"

2025年10月28日 00:50

Introduction: New Data Unveils the "Reality of PHEVs"

"Plug-in hybrids are clean"—this common belief has been challenged by new figures. The European environmental organization Transport & Environment (T&E) analyzed fuel consumption meter data from the European Environment Agency (EEA) and found that the real-world CO₂ emissions of PHEVs average 135g/km. Meanwhile, gasoline and diesel cars emit 166g/km, with the difference being only 19%. U.S. automotive media also reported these findings, stating "PHEVs are almost like gasoline cars," spreading the debate globally. The announcement was made on October 16, 2025, with reports following on October 26. The weight of these numbers is significant. T&E


Lab vs. Road: The Unbridgeable "5x" Gap

The discrepancy between laboratory (WLTP) nominal values and real-world values is an average of 5 times. This is largely due to the overestimation of the "Utility Factor (UF)"—the assumption of how much driving is done electrically. The nominal assumption is 84%, while real data shows 27%. In reality, PHEVs are not running on electricity as much as expected. The gap has widened from "3.5 times" in 2021 to "almost 5 times" in 2023. T&E


The "Blind Spot" of EV Mode: Is the Engine Really Off?

It may be unfamiliar, but the engine operates even in EV mode. In situations where motor output is insufficient, such as uphill or high-speed driving, the internal combustion engine intervenes, consuming an average of 3L/100km of fuel. As a result, EV mode still emits 68g/km of CO₂. This figure is 8.5 times the nominal value, shaking the image of PHEVs "quietly running on electricity alone" to its core. T&E


The Paradox of "Long-Distance EV Range": The Heavier It Gets, The More It Burns

Increasing the battery size to extend the electric range adds weight, worsening fuel efficiency during engine operation. T&E points out that PHEVs with an electric range over 75km tend to emit more CO₂. Extending the range is not a panacea. T&E


Impact on the Wallet: The Invisible "500 Euros a Year"

The data highlights not only environmental impacts. Due to the "hidden fuel consumption" in EV mode and increased engine operation, there is an additional annual cost of 500 euros. Moreover, the average price of a PHEV is 55,700 euros, approximately 15,200 euros higher than the average BEV price in the same year. This represents a "triple burden" on the environment, household, and purchase price. T&E


Manufacturer-Specific Gaps: The Harsh Reality for Prestigious Brands

Mercedes-Benz PHEVs are reported to have a +494% discrepancy compared to nominal values, with the **GLE at +611%, showing an extreme gap between real-world and catalog values. Other major brands also show discrepancies of around +300%**. Even brand myths are equal before real-world data. T&E


The Tug of War Over Rules: 2035 and the "UF Adjustment"

The EU plans to gradually adjust the UF between 2025/26 and 2027/28 to bring it closer to real-world values. However, the industry is pushing for regulatory relaxation to extend the life of PHEVs. According to T&E's estimates, weakening the adjustment could undermine the effect of boosting BEV sales ratios and slow the pace of emission reductions. Policy is now at a crossroads. T&E


What Other Independent Studies Say: ICCT's Overview

The independent ICCT reported in its July 2025 analysis that BEVs reduce lifecycle emissions by 73% compared to gasoline cars. In contrast, hybrids and PHEVs only achieve a 20-30% reduction. The difference in CO₂ emissions from fuel and operational realities creates a "heaven and earth" gap between technologies. Reuters


Media Reception: A Cold Dose of Reality

The UK Guardian reported with the headline "PHEVs emit 5 times the nominal value, reducing only 19%," summarizing the gap between test methods and real-world driving, and issues with consumers, penalty avoidance, and regulations. The news spread from Europe to the world, becoming material for policy discussions. The Guardian


Snapshot of Social Media Reactions (Summary)

  • Reddit (r/electricvehicles)
    Criticism of "headline exaggeration" with comments like "'almost the same' is an overstatement. Numerically, it's about 25% less." On the other hand, realists argue, "it's expected since many don't charge." The debate split into two axes: "user behavior" and "headline expression." Reddit

  • Reddit (Various National Communities)
    In German-speaking areas, reactions like "68g/km even in EV mode is surprising" were prominent, spreading doubts about PHEV design philosophy. Article sharing continued in the Irish community as well. Reddit

  • X (formerly Twitter)
    Some users expressed distrust towards T&E, with sarcastic comments like "Are the means of transport used by activists really zero-carbon?" Conversely, there were also voices calling for policy strengthening based on data. *Individual post texts are briefly quoted and summarized. X (formerly Twitter)

  • Spread of News/Videos
    Covered by Australian EV media and YouTube, the figures of 19% reduction and 5x discrepancy made for "headline-worthy" content, expanding the debate. The Driven

How to Interpret: Three Points of Discussion

  1. More of an "Operational" Issue than a "Technical" One
    Charging frequency, driving patterns, and vehicle weight influence results. Unless PHEVs are operated under "ideal conditions," they won't achieve the expected reductions. T&E

  2. The Limitations as a "Bridge to Transition"
    If regulations are relaxed to preserve PHEVs, it could slow the adoption of BEVs. The EU's UF adjustment is effective at least for "visualization." T&E

  3. Consumer Practicality
    Vehicle prices remain high, with an additional annual cost of 500 euros. From both household and sustainability perspectives, there is now material to reconsider BEV/HEV. T&E

If You Still Choose PHEVs: Key Points for Damage Control (Practical Suggestions)

  • Charge daily (ensure availability at work/home).

  • Choose designs with "EV-focused" high-output motors.

  • Be cautious of the "paradox" of heavy SUVs + long-distance EV range.

  • Use driving logs or fuel efficiency apps to visualize the EV mode ratio.

  • Account for fuel efficiency deterioration in winter heating/high-speed operations. (The above is a practical summary by the author. The latest trends in regulations, prices, and power mixes depend on national circumstances.)



Interview Notes (Key Figures)

  • Real-world CO₂: PHEV 135g/km, ICE 166g/km → −19%.

  • Lab vs. Real-world: Approx. 5x discrepancy.

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