A vertical heat recovery steam generator, the low-pressure stages of which are designed as a once-through system, having a condensate preheater with at least one condensate preheater heating surface, through which a flow medium flows and which is disposed in a hot gas channel through which hot gas flows, a low-pressure preheater with at least one low-pressure preheater heating surface through which the flow medium flows and which is disposed in the hot gas channel, and a low-pressure evaporator with at least one low-pressure evaporator heating surface through which the flow medium flows and which is disposed in the hot gas channel. The flow medium flows successively through the at least one low-pressure preheater heating surface and the at least one low-pressure evaporator heating surface in one pass and without additional pressure compensation.