A roof-mounting solar energy collection unit comprises: collector, storage unit, fluid flow and return lines, and controls for the extracted fluid temp.. In the new design, the storage unit (2) is constructed as a flat plastic tank, with a slot opening (11) on one side, into which one end of the collector (1) projects, making a permanent watertight connection. The collector is a sack-like vessel, consisting of a fabric coated on both sides by plastic. It (1) is so constructed, that a given fluid volume is distributed over maximal area, and led under negligible pressure into the storage tank (2).    The collector has two rectangular fabric sections of the same shape, which are permanently connected and sealed watertight on two edges. The joins are welded, and tucked into the interior. The ends opposite the tank are sealed by a tubular section (3) of at least the collector width. Inside the collector this tube has spaced openings (10), and at one end there is a water supply connection, whilst the other is closed. The collector is glued to the tube, which is used to tension it. The other end of the collector enters the tank, and one half is glued to its base, the other to its inner face. Pref. black pool liner is used as the collector material. The flat tank (2) has rounding and angles, to deflect the wind, and it is heat insulated (12). Styrofoam slabs may be used for this, in two offset layers completely encasing the tank. For both heat insulation, and to level collector and tank, similar insulation is placed under the collector.    USE -   A solar collector heating and storing water on the roof.    ADVANTAGE -   This unit compares well with conventional devices in material and construction costs. It takes up little space in storage and transport, and is easy to handle, esp. during installation on roofs. No special expertise is required for mounting, and conventional equipment is used in mfr.. Precautions are included to prevent heat losses, and to defend against high winds. The lower fastening tube of the collector usefully also performs sealing, water inlet and distribution functions.