Abstract: A method of manufacturing an integral one-piece solar collector panel 10 by a rotational moulding process is disclosed. The solar collector panel 10 has a plurality of fluid ways 15 extending between opposed ends 18, 19 and transverse headers 18, 19 opening into the open ends of the fluid ways 15. The panel 10 is moulded by a rotational moulding process using mould faces with a non planar topography, eg in the form of a plurality of lines projecting outwardly proud of the remainder of the mould plate. This enables areas of the moulded body 12 to be formed that are not hollow and form a solid wall in the moulded panel and other areas of the body to be formed that are hollow and form the fluid ways 15 and headers 18, 19. After the moulding of the panel 10 has taken place the two opposed mould faces are moved towards each other to cause the contacting layers of mould material to firmly adhere to each other.