Abstract: A solar energy heating or cooling system and method of performing the same is disclosed comprising a solar collector mechanism disposed generally on the roof of the structure for which it is to be used and supplied internally with a heat transfer medium of the halogenated hydrocarbon family having characteristics permitting expansion from a liquid to a gas, the collector mechanism being connected to an energy storage means having a plurality of conduit means disposed therewithin and connected to a reservoir for collection of a liquid, the liquid being pumped back to the solar collector mechanism by a pump for expansion into a gas, with control means being connected between the solar collector mechanism and the pump for controlling the level of the heat transfer medium.