A method for releasing heat, the method comprising: (pa1) crystallizing a heat storage material containing sodium acetate trihydrate; (pa2) melting the heat storage material at a temperature of not more than 80 degrees Celsius after the step (pa1); (a) cooling a heat storage device comprising the heat storage material to bring the sodium acetate trihydrate into a supercooled state; wherein the heat storage device comprises: a first electrode having a surface which is in contact with the heat storage material , wherein the surface is formed of at least one selected from the group consisting of silver, a silver alloy, and a silver compound; a second electrode in contact with the heat storage material ; a power supply for applying a voltage to the first electrode and the second electrode ; and characterized in that an inorganic porous material is contained in the heat storage material ; the inorganic porous material has an average pore diameter of not less than 10 nanometers and not more than 50 nanometers; and the inorganic porous material is formed of silica gel; the method is further characterized by : (b) applying a voltage to the first electrode and the second electrode with the power supply at a temperature of not more than 58 degrees Celsius after the step (a) to release the heat from the heat storage material ; and (c) heating the heat storage device at a temperature of not less than 58 degrees Celsius and not more than 80 degrees Celsius to melt the sodium acetate trihydrate after the step (b). (pa1) crystallizing a heat storage material containing sodium acetate trihydrate; (pa2) melting the heat storage material at a temperature of not more than 80 degrees Celsius after the step (pa1); (a) cooling a heat storage device comprising the heat storage material to bring the sodium acetate trihydrate into a supercooled state; (a) cooling a heat storage device comprising the heat storage material to bring the sodium acetate trihydrate into a supercooled state; wherein the heat storage device comprises: a first electrode having a surface which is in contact with the heat storage material , wherein the surface is formed of at least one selected from the group consisting of silver, a silver alloy, and a silver compound; a second electrode in contact with the heat storage material ; a power supply for applying a voltage to the first electrode and the second electrode ; and a first electrode having a surface which is in contact with the heat storage material , wherein the surface is formed of at least one selected from the group consisting of silver, a silver alloy, and a silver compound; a second electrode in contact with the heat storage material ; a power supply for applying a voltage to the first electrode and the second electrode ; and characterized in that an inorganic porous material is contained in the heat storage material ; the inorganic porous material has an average pore diameter of not less than 10 nanometers and not more than 50 nanometers; and the inorganic porous material is formed of silica gel; the method is further characterized by : (b) applying a voltage to the first electrode and the second electrode with the power supply at a temperature of not more than 58 degrees Celsius after the step (a) to release the heat from the heat storage material ; and (c) heating the heat storage device at a temperature of not less than 58 degrees Celsius and not more than 80 degrees Celsius to melt the sodium acetate trihydrate after the step (b). (b) applying a voltage to the first electrode and the second electrode with the power supply at a temperature of not more than 58 degrees Celsius after the step (a) to release the heat from the heat storage material ; and (c) heating the heat storage device at a temperature of not less than 58 degrees Celsius and not more than 80 degrees Celsius to melt the sodium acetate trihydrate after the step (b). <EOS>