To demonstrate that linear interpolation of charges is computationally more efficient than linear interpolation of the potential energy functions for systems with many titratable sites, we investigated how the computational cost of a simulation scales with the number of titratabe sites in the system for both approaches. Because we have implemented interpolation of the charges rather than potentials into the fork of GROMACS 2021 release, whereas the potential interpolation was implemented in a fork of GROMACS 3.3 release, we compare the relative performances of both codes for an increasing number of titratable sites in the system. We define the relative performance as the ratio between the average wall-clock time per integration step for a simulation with constant pH on the one hand and the average wall-clock time per integration step for a normal simulation without constant pH on the other hand.