Abstract: To improve the efficiency of a condenser-side-storage solar heat-pump system, the controller for the heat pump measures the temperature outside the house and: (1) subtracts it from the temperature within a collector for the solar heat system; and (2) adds the product of a minimum temperature which is set for the solar heat system storage in accordance with the season and a constant factor. If this sum is greater than the product of storage temperature and the same constant factor, the heat pump is run. This mode of operation causes the heat pump to: (1) store to higher temperatures during full sun conditions; (2) run continuously during low storage conditions; and (3) bias towards sunny weather operation.