We attempted to design a capsule type heat storage system, which can store heat with warm water 333 K and can produce warm water lover 320 Ii directly from the heat storage tank. We developed a new PCM with melting point 323 K and heat of fusion 205 kJ/kg. This PCM was obtained by adding sodium nitrate to sodium acetate trihydrate. It is found that this PCM melted with warm mater of 333 K and crystallized at 321 K. Also, it was found that heat quantity and melting point of this PCM didn't change even if freezing and melting was repeated 1,100 times. We carried out characteristics evaluation of this system. It was found that this system could store heat with warm water (333 K) within 10 hours. So, this system is able to use off peak discount electric power. The theoretical heat storage quantity of this system is 322 MJ and the experimental value was 305 MJ in this evaluation. So, it is understood that this system could store heat almost equal to the theoretical value. Also, it was found that this system could produce warm water over 320 K, which is required space heating, and can release almost stored heat.