POWER STORAGE SYSTEM

[PROBLEM] The deterioration state of an electric storage apparatus may be changed depending on the usage environment of the electric storage apparatus. [SOLVING MEANS] An electric storage system includes an electric storage apparatus (10) connected to a load and performing charge and discharge, a temperature sensor (12) detecting the temperature of the electric storage apparatus in response to connection of the electric storage apparatus to the load, and a controller (30) estimating the deterioration state of the electric storage apparatus based on temperature information in a usage environment of the electric storage apparatus. The controller obtains a temperature distribution of the electric storage apparatus based on an output from the temperature sensor when the electric storage apparatus is connected to the load, and specifies a usage environment of the electric storage apparatus associated with the obtained temperature distribution.