This depends on the size of the gym, that is, the total number of people that can be accommodated at a time. If it is a long-term investment in fixed assets, it is best to use solar energy with larger capacity. However, if it is open 24 hours a day, the flow of people is large, and the gym carries out tasteful content, it is best to use a small hot water boiler with an insulated hot water tank to supply hot water 24 hours a day.