with a simple algorithm for fore- casting the building's energy needs 24 hours in advance. The savings vary, de- pending on the local utility's rate struc- ture, the building materials and the performance of the cooling system un der different load conditions. Obvious ly, the better insulated the structure is the more its thermal storage capacity exploited. In Sweden thermal storage is utilized during the winter. All new office build- ings are well insulated and store"free" heat the heat generated by people lights, office equipment and incoming sunlight. Whereas most office buildings in the U.S. have thin walls and cool quickly during a winter night, Sweden ell insulated offices that store free heat during the day and overnight. By storing heat in the walls, floors and eilings, the building becomes almost self-sufficient and thus does not need a Central heating system