One of the most efficient uses of solar energy is that of warming water. With a high density and heat capacity, water is an excellent medium for storing the sun's energy. NSESI offers a range of water heating systems, from direct heating systems that circulate water through the collectors (best in climates that never freeze) to heat pipe collectors that can use antifreeze liquid circulated through a heat exchanger to warm water stored in a remote tank (capable of being used in the most extreme environments). Because water heating is a very efficient use of solar energy, significant heating can be achieved using just one or two collectors.