With this objective, we here compare three distinct theoretical approaches to study the electrified Pt(111)water interface: i) FF-CMD simulations where interfacial electrification is achieved by introducing excess electrons on the metal electrodes and compensating counter charges by partially charged hydrogen atoms, ii) DFT-AIMD simulations with partially charged hydrogen atoms and iii) DFT-AIMD simulations with a homogeneous background charge. Our analysis of bias potential and interfacial water response clarifies that electron transfer into interfacial water is key to understand the magnitude of the observed capacitances and, as a result, to rationalize the failure of FF-CMD simulations which inherently miss the according component. In addition, our results directly connect to the ubiquitous observation of partial ionic charge in interfacial water which highlights the limited realism of traditional electrochemical models that assume a priori integer charges aka oxidation states of species, even when localized in the interfacial region. Electrification is achieved by introducing an electronic excess charge q = -eN e leading to some charge density distribution ρ electrode within the metallic region of the system and a nominal area density σ = q/A, where A = 2×82.3 Å2 is the total surface area of the symmetric slab. The counter charges needed to maintain the overall charge neutrality of the supercell are introduced using two distinct methods: On the one hand we use a Homogeneous Background Charge Method (HBG) as in a range of previous works . This leads to a homogeneous and isotropic counter charge density ρ counter = eN e /V , where V = 8.443 × 9.749 × 27.894 Å3 is the supercell volume. On the other hand, we use a Partially Charged Hydrogen Method (PCH) by slightly modifying the core charges of all N H hydrogen atoms in the system, i.e. in the water molecules , by ∆q H = eN e /N H . As a result counter charges are only introduced within the solvent region of space, with the counter charge density given by the hydrogen density ρ H via ρ counter = ∆q H × ρ H . Both charging methods have the advantage that counter charge distributions equilibrate on the same timescale as the water density distribution, i.e. within accessible simulation times of ∼ 30 ps. At the same time we eliminate consciously ion-specific differences in the counter charge distribution. We perform canonical DFT-AIMD simulations at finite excess charge using both approaches -HBG and PCH -as well as FF-CMD simulations using the SPC/E water model with the PCH method implemented via modified hydrogen partial charges (0.4238 + ∆q H ) and excess electrons treated via the constant charge (ConQ) method .