Electric power plants account for approximately half the global industrial water withdrawal. Although continued electric-sector expansion is probable, significant variations in water intensity by electricity technology and cooling system type make its effect on water demands uncertain. Using GCAM, an integrated assessment model of energy, agriculture, and climate change, we establish lower-, median-, and upper-bound estimates for current electric-sector water withdrawals and consumption in 14 geopolitical regions, comparing them with available estimates. We then explore water use for electricity to 2095, focusing on uncertainties in water withdrawal and consumption intensities, power plant cooling system changes, and adoption rates of water-saving technologies. Results reveal a probable decrease in the water withdrawal intensity with capital stock turnover, but a corresponding increase in consumptive use, for which technologies under development may compensate. At a regional scale, water use varies significantly based on the existing capital stock and its evolution over the century.