Device for a building, said device comprising a storage element for storing a first fluid, a circuit for circulating the first fluid that is connected to said storage element, and a heat pump comprising an evaporator and a condenser, the circuit comprising at least one configuration for simultaneously charging a first-cold-fluid storage part within the storage element and a first-hot-fluid storage part within the storage element, in the simultaneous charging configuration: - the heat pump is configured to form a cold source at the evaporator intended to participate in the charging of the first-cold-fluid storage part and a hot source at the condenser intended to participate in the charging of the first-hot-fluid storage part when first fluid from the storage element is circulated in the circuit, - the circuit is configured such that, when the first fluid from the storage element is circulated in the circuit, a first fraction of said first fluid circulating in the circuit experiences an increase in temperature induced by the use of the heat pump before being introduced into the storage element at the first-hot-fluid storage part, and a second fraction of the first fluid circulating in the circuit experiences a reduction in temperature induced by the use of the heat pump before being introduced into the storage element at the first-cold-fluid storage part, characterized in that it comprises a loop for circulating a second fluid, said loop being associated: • with the evaporator of the heat pump so as to cool the second fluid when the heat pump is used, • with a first heat exchanger through which there passes, in the simultaneous charging configuration, the second fraction of the first fluid such that said second fraction of the first fluid experiences, at said first heat exchanger, said reduction in temperature linked with the use of the heat pump with the aid of the second fluid after its passage through the evaporator. - the heat pump is configured to form a cold source at the evaporator intended to participate in the charging of the first-cold-fluid storage part and a hot source at the condenser intended to participate in the charging of the first-hot-fluid storage part when first fluid from the storage element is circulated in the circuit, - the circuit is configured such that, when the first fluid from the storage element is circulated in the circuit, a first fraction of said first fluid circulating in the circuit experiences an increase in temperature induced by the use of the heat pump before being introduced into the storage element at the first-hot-fluid storage part, and a second fraction of the first fluid circulating in the circuit experiences a reduction in temperature induced by the use of the heat pump before being introduced into the storage element at the first-cold-fluid storage part, • with the evaporator of the heat pump so as to cool the second fluid when the heat pump is used, • with a first heat exchanger through which there passes, in the simultaneous charging configuration, the second fraction of the first fluid such that said second fraction of the first fluid experiences, at said first heat exchanger, said reduction in temperature linked with the use of the heat pump with the aid of the second fluid after its passage through the evaporator.