The objective of this study is to examine the accuracy of the absolute gravity potential estimated at the clock network stations when clock measurements are combined with absolute gravity potential values. For this purpose, we developed a Monte Carlo (MC) simulation procedure for a network consisting of 20 optical clocks, each collocated with a GNSS receiver and located in Europe. The clock observations were generated as synthetic gravity potential differences between clock stations based on the EGM2008 Global Geopotential Model (GGM), incorporating white and correlated noise. The errors for the absolute values were simulated considering the diagonal part of their Stokes coefficient covariance matrix, as well as the covariance matrix of the estimated coordinates of the GNSS stations. The MC procedure applies the least squares approach to the combination of relative clock measurements and absolute gravity potential (pseudo) observations. The results show that combining relative clock measurements with GGM-based datum constraints can improve the accuracy of the estimated station potentials by about 57-85% relative to the median commission-error level of the adopted GGMs, depending on the constrained stations and their commission-error magnitudes. However, the achievable absolute accuracy remains limited by the GGM commission errors at the constrained stations and is often insufficient for \(10^{-18}\) level clock applications.