Device for heating a treatment fluid for a laundry treatment appliance, in particular a washing machine or a washer-dryer, said device comprising the following features: an input-side recirculation interface for conducting the treatment fluid out of a laundry treatment chamber of the laundry treatment appliance; an evaporator which is designed to evaporate a liquid coolant using a fluid for providing thermal energy and to provide said coolant as a gaseous coolant; a condenser which is designed to heat the treatment fluid using the gaseous coolant and to provide said treatment fluid as a heated treatment fluid; and an output-side recirculation interface for conveying the heated treatment fluid away to the laundry treatment chamber, comprising an input-side process air interface for conducting process air out of the laundry treatment chamber, the condenser or an additional condenser being designed to heat the process air using the gaseous coolant and to provide said air as heated process air, and having an output-side process air interface for conveying the heated process air away to the laundry treatment chamber, characterised by an input-side fluid interface for conducting the fluid and having an input-side distribution means which is designed to couple the input-side fluid interface to the evaporator in a first operating state and to couple the input-side process air interface to the evaporator in a second operating state, the evaporator being designed to evaporate the liquid coolant using the fluid and provide said coolant as the gaseous coolant in the first operating state, and to evaporate the liquid coolant using the process air and provide said coolant as the gaseous coolant in the second operating state. an input-side recirculation interface for conducting the treatment fluid out of a laundry treatment chamber of the laundry treatment appliance; an evaporator which is designed to evaporate a liquid coolant using a fluid for providing thermal energy and to provide said coolant as a gaseous coolant; a condenser which is designed to heat the treatment fluid using the gaseous coolant and to provide said treatment fluid as a heated treatment fluid; and an output-side recirculation interface for conveying the heated treatment fluid away to the laundry treatment chamber, comprising an input-side process air interface for conducting process air out of the laundry treatment chamber, the condenser or an additional condenser being designed to heat the process air using the gaseous coolant and to provide said air as heated process air, and having an output-side process air interface for conveying the heated process air away to the laundry treatment chamber, characterised by an input-side fluid interface for conducting the fluid and having an input-side distribution means which is designed to couple the input-side fluid interface to the evaporator in a first operating state and to couple the input-side process air interface to the evaporator in a second operating state, the evaporator being designed to evaporate the liquid coolant using the fluid and provide said coolant as the gaseous coolant in the first operating state, and to evaporate the liquid coolant using the process air and provide said coolant as the gaseous coolant in the second operating state.