Our second example illustrates the simulation of an explicitly solvated Au(111) interface presented in Figure using both constant inner potential (CIP-DFT) and constant charge (canonical DFT) molecular dynamics (MD). Overall, the results given in Figure demonstrate that CIP-DFT-MD calculations can be readily performed to study the dynamics of explicitly solvated electrochemical interfaces and that even moderately large systems can be treated to address interfacial properties under constant (inner) potential conditions. By comparing the number of MD steps in constant potential and constant charge simulations against wall-time, the constant potential simulation was observed to be ∼20-25% more time consuming -constant potential calculations are not prohibitively expensive as sometimes presumed. Figure shows Figure demonstrates that constant potential CIP-DFT-MD simulations of an explicitly solvated interface exhibit substantial charge fluctuations. Even though most simulations focus on thermodynamic expectation values, it needs to be stressed that variations and fluctuations are fundamental properties of statistical thermodynamic systems and must be captured to ensure thermodynamic consistency. While the same thermodynamic expectation values can be obtained from either grand canonical or canonical simulations, the other quantities cannot. For instance, time-dependent fluctuations around an equilibrium value determine important electrochemical quantities such as capacitance, electric conductivity, and reaction rates. The fluctuations and averages can be captured with MD simulations but the calculations need to be done by enforcing the relevant thermodynamics constraints, such as constant temperature and electrode potential, used experimentally. Further evidence for the importance of using the correct ensemble is provided by the sensitivity of electrochemical kinetics to the electrode potential and surface charge, , role of fluctuations in adsorption energies , the energy gap fluctuations determining the reaction rate of Marcus-like (proton coupled) electron transfer theories. Hence, MD simulations of electrochemical systems should be performed in the GCE to achieve fully consistent treatment of electrochemical interfaces and reactions.