Recently, Korea has become increasingly interested in unused, but possibly useful energy resources, due to the world-wide controversy over nuclear power and limitations in renewable energy production. Among these unused resources, the water that is produced in our surroundings is available as a potential energy source for heating, cooling and domestic hot water. This water is relatively stable on the supply side, available as a high-efficiency source in all seasons, and is continuously replenished without polluting the environment. This paper analyses the energy savings generated based on the actual use of a sustainable heating and cooling system that operates using the water escaping from a nearby building. The results indicate the value of protecting the environment as well as reducing energy consumption and associated costs.