In a steam power plant, the exhaust steam after the steam turbine is discharged to a condenser. In the condenser, the steam is cooled by the cooling water and converted to condensate. The latent heat of the phase change from the steam to the condensate is transferred to the cooling water and discarded to atmosphere in the cooling tower. Therefore, a large quantity of the latent heat is wasted. This paper proposes a cogeneration using a hot water system working with the cooling water system in the condenser, which can partially recover the latent heat. The hot water is used as an energy input for an absorption chiller in the HVAC system. In such a cogeneration, keeping the power output of the steam power plant free from the load change of the absorption chiller is a challenge. The paper presents the system configuration and working mechanism of the proposed cogeneration plant. The system applies two 3-way control valves installed on the cooling water piping system and the hot water piping system, respectively. The valves are manipulated to accommodate the flow rates of the cooling water and hot water to avoid the impact from the load change of the absorption chiller to the steam power output. In the paper, the flow rate accommodation and energy balance between the cooling water and the hot water are illustrated. The total thermal energy balance conducted among the exhaust steam, cooling water flow, hot water flow, and condensate is presented. The cogeneration plant utilization factor μ and energy saving ratio φ upon the percentage of the latent heat recovered are discussed. Also, an application example is shown in the paper to help understand the proposed cogeneration and energy balance comprehensively. The study shows such a cogeneration combined the steam power plant with the absorption chiller in the HVAC system is practical and economically justified which will be expected.