Below is a list of Electric Furnaces manufacturers from Gary, Indiana. An electric furnace is an enclosed structure that uses electricity as a heat source to produce high temperatures for industrial purposes. In these furnaces, electricity is used to generate the heat and then push the air out through the central system. These furnaces can be made with several kinds of heat resistant (refractory) elements in order to withstand long term use. The enclosed space holds the materials, gas or air being heated until the desired temperature is reached.