A method for manufacturing a composite insulated panel (1) comprising the steps of: providing a first sheet (2); cutting a hole (7) in the first sheet (2) to accommodate a photovoltaic solar collector module (8); inserting the solar collector module (8) into the cut-out hole; sealing the solar collector module to the first sheet (2); providing a second sheet (3), the second sheet having an opening therein to receive a connector housing (22); leading electrical connections from the solar collector module through the connector housing; and providing a body (4) of insulating material between the inner face of the second sheet and the inner face of the first sheet and the inner face of the photovoltaic solar collector module.