A condensing heat recovery steam generator (cHRSG) includes a main stack for an exhaust hot gas main flow, a bypass stack for allowing a fraction of exhaust hot gas to bypass the exhaust hot gas main flow, and a heat pump. The cHRSG includes a primary water circuit, a secondary water circuit, and a tertiary water circuit. The cHRSG additionally includes a feedwater line, a first heat exchanger for providing heat exchange between the feedwater line and the secondary water circuit, and a second heat exchanger for providing heat exchange between the primary water circuit and the tertiary water circuit. In the cHRSG, latent heat is partially recovered from said exhaust hot gas circulating in the bypass stack through the second heat exchanger and additional heat is extracted in the tertiary water circuit by said heat pump, contributing to a preheating performed in a preheater of the primary water circuit.