The alternative scheme is based on a linear interpolation of partial charges, 14 rather than the potential energy functions as in the original implementation of constant pH MD in a GROMACS fork. Although the previous implementation of constant pH in a GROMACS fork was documented and shared with the community as an open-source program, there has been some misunderstanding about how electrostatic interactions were computed for λ-particles. To resolve this, we first explain in detail how the electrostatic interactions were calculated in the previous GROMACS implementation of constant pH MD. We next contrast this linear interpolation between the potential energy functions of the protonated and deprotonated states of a residue, with the interpolation between the partial charges of both states, and show why the latter is computationally much more efficient. We then demonstrate the superior performance of the charge-interpolation scheme by running a series of constant pH MD simulations of amino acids and proteins. To emphasize that the new constant pH implementation in GROMACS is not linked to a specific force field or method for evaluating electrostatic interactions, we also show the results of constant pH MD simulations with the Martini coarse-grained force field. Because of GROMACS' large user community, we expect our work to increase popularity of constant pH MD simulations.