Abstract: A solar energy collector connectable with a fluid-circulating system is contained in a plenum within an insulative housing and has a plurality of generally parallel, heat-absorbing conduits extending between intake and outlet manifolds and confronting the sun or other heat source through a transparent window, each conduit being separated from an adjacent conduit by an intervening slot. Positioned below the conduits is a heat-absorbing tank which is connected in fluid-flow relationship with the outlet manifold and also with the circulation system so that a heat-transfer medium may flow continuously between the energy collector and the circulation system. The tank receives radiant energy through the slots and after absorbing some of the radiation reflects the remaining portion upwardly to the conduits to thereby increase radiation intensity on and heat absorption by the conduits. Multiple reflections between tank and conduits further increase energy absorption both by tank and conduit.