A study by the International Council on Clean Transportation (ICCT) revealed that plug-in hybrid vehicles registered in Europe in 2023 emitted, on average, 4.6 times more carbon dioxide (CO2) in real-world conditions than the values listed during their official approval process. The research examined the real-world performance of about 920,000 plug-in hybrid vehicles registered in Europe between 2021 and 2023. For vehicles registered in 2023, the actual emissions were significantly higher than the official figures. This gap is due to how official emissions are calculated and the actual proportion of kilometers driven using electricity. During the European WLTP (World Harmonized Light Vehicles Test Cycle) homologation process, results from different operating conditions are combined using a parameter called the "utility factor," which is meant to represent the statistical share of kilometers driven mainly using electricity. However, real-world data shows that drivers, on average, use the electric mode much less than the regulatory calculation assumes. This causes the internal combustion engine to operate more frequently than expected, leading to higher real emissions. This effect is especially noticeable when a driver rarely recharges the vehicle or regularly makes long trips that exceed the electric range. The real-world performance of each plug-in hybrid can vary greatly depending on how it is used. The same model can have very different emission profiles based on driving habits. The effectiveness of a plug-in hybrid depends strongly on how it is used in practice. A driver who regularly recharges the vehicle and makes short trips within the electric range can drive most of their kilometers using electricity, minimizing the use of the internal combustion engine. In contrast, if the battery is rarely recharged, the vehicle functions more like a traditional gasoline-powered car. On long trips, especially on highways, fuel consumption can be significantly higher than the official value on the technical sheet suggests. Not all vehicles labeled "hybrid" function the same way. A conventional hybrid, or HEV (Hybrid Electric Vehicle), generally has a small battery that is recharged mainly through the internal combustion engine and energy recovery during braking. A plug-in hybrid, or PHEV (Plug-in Hybrid Electric Vehicle), has a much larger battery that can be recharged at home or at charging stations. Depending on the model, a PHEV can travel several dozen kilometers using mainly electricity before the internal combustion engine is more frequently used. The European Union is revising its calculation method to better reflect the actual use of plug-in hybrids. The goal is to ensure that the values displayed during homologation more closely match the emissions drivers can expect on the road. This change will also help drivers more accurately compare a plug-in hybrid with a conventional gasoline vehicle, a conventional hybrid, or a fully electric vehicle. Before purchasing a PHEV for its low emissions, the key question should not only be "how much does it consume?" but also: how many of my daily kilometers could I actually drive using electricity, and can I regularly recharge? This answer, rather than the number on the homologation sheet, will determine the vehicle's actual consumption and emissions.