Heating with a heat pump

House heating by extraction of heat from the earth through a circulating refrigerant has proved practical and economically feasible in a test conducted during one season in Indianapolis, Ind., according to an article by A. C. Crandall, vice-president, Indianapolis Power and Light Company, Indianapolis, in Electrical World for November 9, 1946. Records show that during the 8-month heating season, although outside temperatures dropped as low as ten degrees below zero, inside temperature was maintained at a constant 72 to 74 degrees.