Water heating is the process of turning water into a hot liquid. It can be done with an electric coil, by heating it through the use of a vacuum, or it can be heated through solar power. There are three methods of water heating: 1. A water heater coil heats up the cold water that is sent to it by electricity or gas heaters. 2. Electric heaters can work either in a heat pump or in a vented system. 3) Solar power heats up water during through the process of evaporation and condensation.