The dramatic increase in the price of energy since 1973 has revived interest in a number ofold but still valid ideas of how to utilize energy in a more efficient manner. The ice-makerheat pump is a prime example of already-existing, energy efficient equipment that could beused to provide heat for space heating and water heating. The ice that is formed as a byproductduring operation of the heat pump in the heating cycle can be discarded, sold, orstored for later use, as dictated by energy policy considerations or economics.

The greatest overall energy efficiency of the ice-maker heat pump system is realized whenthe harvested ice is stored and used to cool the building in the summer months. When theseasonal heating and cooling loads of a building are balanced in this manner, an Annual CycleEnergy System (ACES) results. In this paper, different modes of operation of an ice-makerheat pump system are examined with respect both to their energy savings and to their rate ofreturn on investment. Particular attention is given to those systems which not only providea reasonable rate of return based on current energy price levels, but which also offerflexibility in attaining even greater energy and cost savings as economic conditions andenergy policies change. Applications of the ice-maker heat pump that are today only marginallyeconomic may become much more attractive as higher energy costs and new utility rate structurescome on the scene.