A heat recovery steam generator comprising: a casing having an inlet and an outlet and a gas flow path there between for gas flow upstream from the inlet toward the outlet downstream therefrom; low pressure evaporator coils (77, 77', 77") of heat exchanger tubes, the low pressure evaporator coils (77, 77', 77") located within the casing downstream from the inlet; preheater booster coils (74, 74', 74") of heat exchanger tubes, the preheater booster coils (74, 74', 74") located within the casing downstream from the casing inlet and upstream of the low pressure evaporator coils (77, 77', 77"), so that gas passing through the inlet can flow downstream to pass through the preheater booster coils (74, 74', 74"), and gas passing through the preheater booster coils (74, 74', 74") can flow downstream therefrom; feedwater heater coils (80, 80', 80") of heat exchanger tubes, the feedwater heater coils (80, 80', 80") located within the casing downstream from the low pressure evaporator coils (77, 77', 77") so that gas passing through the low pressure evaporator coils (77, 77', 77") can flow downstream from the low pressure evaporator coils (77, 77', 77") to pass through the feedwater heater coils (80, 80', 80"); a water to water heat exchanger (125, 125', 125") having a low temperature path (130, 231, 330) and a higher temperature path (140, 258, 140"); a first conduit (138, 255, 138") extending from flow connection with the preheater booster coils (74, 74', 74") to flow connection with the high temperature path (140, 258, 140") of the water to water heat exchanger (125, 125', 125"), the first conduit (138, 255, 138") configured for water to flow there through from the preheater booster coils (74, 74', 74") to the water to water heat exchanger (125, 125', 125"); and a second conduit (135, 252, 135") extending from the feedwater heater coils (80, 80', 80") to the preheater booster coils (74, 74', 74") of heat exchanger tubes, the second conduit (135, 252, 135") configured to allow water to flow there through from the feedwater heater coils (80, 80', 80") to the preheater booster coils (74, 74', 74"). a casing having an inlet and an outlet and a gas flow path there between for gas flow upstream from the inlet toward the outlet downstream therefrom; low pressure evaporator coils (77, 77', 77") of heat exchanger tubes, the low pressure evaporator coils (77, 77', 77") located within the casing downstream from the inlet; preheater booster coils (74, 74', 74") of heat exchanger tubes, the preheater booster coils (74, 74', 74") located within the casing downstream from the casing inlet and upstream of the low pressure evaporator coils (77, 77', 77"), so that gas passing through the inlet can flow downstream to pass through the preheater booster coils (74, 74', 74"), and gas passing through the preheater booster coils (74, 74', 74") can flow downstream therefrom; feedwater heater coils (80, 80', 80") of heat exchanger tubes, the feedwater heater coils (80, 80', 80") located within the casing downstream from the low pressure evaporator coils (77, 77', 77") so that gas passing through the low pressure evaporator coils (77, 77', 77") can flow downstream from the low pressure evaporator coils (77, 77', 77") to pass through the feedwater heater coils (80, 80', 80"); a water to water heat exchanger (125, 125', 125") having a low temperature path (130, 231, 330) and a higher temperature path (140, 258, 140"); a first conduit (138, 255, 138") extending from flow connection with the preheater booster coils (74, 74', 74") to flow connection with the high temperature path (140, 258, 140") of the water to water heat exchanger (125, 125', 125"), the first conduit (138, 255, 138") configured for water to flow there through from the preheater booster coils (74, 74', 74") to the water to water heat exchanger (125, 125', 125"); and a second conduit (135, 252, 135") extending from the feedwater heater coils (80, 80', 80") to the preheater booster coils (74, 74', 74") of heat exchanger tubes, the second conduit (135, 252, 135") configured to allow water to flow there through from the feedwater heater coils (80, 80', 80") to the preheater booster coils (74, 74', 74").