a self - contained apparatus for collecting , storing and transmitting solar heat includes an elongated rectangular insulated housing in which a quantity of heat retaining material is confined and a collector on the horizontal and vertical faces of the housing which has only one layer of glass for each face through which solar heat may pass and be collected upon a heat - collecting surface . a conditioning pump is provided within the apparatus to circulate conditioning air through both the collector and the heat retaining material within the housing so that heat is transferred from the collector to the heat retaining material . specially designed and positioned ducts connect the collector to the interior of the housing in a manner such that air interchange between the collector and the interior of the housing is prevented except during operation of the conditioning pump . both the collector and the interior of the housing are provided with appropriately positioned baffles to expose the conditioning air to all of the heat retaining material . utility pump means are also provided in the apparatus for withdrawing heat from the heat retaining material and circulating it through a remote building structure .