A series-parallel condensing system comprised of an air-cooled condenser, a surface condenser, a circulating water system and a cooling tower, body of water, or other equivalent heat sink. The cooling tower, being an evaporative device, consumes water. In the simplest embodiment of the invention steam is condensed in a two-stage series process with steam first fed to an air-cooled condenser where the majority of the steam is condensed and then to a surface condenser, which in conjunction with the circulating water system and cooling tower condenses the remaining steam. This embodiment achieves the greatest degree of water conservation. The function of the surface condenser is to replace the dephlegmator of the air-cooled condenser, which results in a significant reduction in the size and cost of the air-cooled condenser and also yields improved plant performance and operational simplicity. In a second embodiment, where additional makeup water is available, a steam bypass system is added converting the system from a series condensing process into a series-parallel process. In this arrangement steam exiting the turbine flows through both the air-cooled condenser and also through the bypass system with final condensation taking place in the surface condenser.