A solar energy collecting panel for heating by solar radiation a liquid culating in a section of piping and constituted by a flat rectangular box thermally closed by a cover transparent to solar radiation and containing the said section of piping. The said box is constituted by a stamped metal sheet whose surface is less than 1 m squared and also contains a stamped copper tray in intimate contact with the piping section, the said tray supporting by itself the transparent cover and being thermally spaced from the box, the insulating pad being constituted by a in situ moulded block of rigid foam. Such a panel is intended to be used for feeding a central heating system and/or a hot water distribution system, especially for household purposes or swimming pools.