A method of repurposing dual-paned insulated glass window units (IGUs) that would otherwise be put to waste into thermal solar panels capable of generating hot water for a residence or other structure. The method includes the steps of removing an existing IGU, disassembling and cleaning the IGU, and reassembling the IGU with a new silicon seal and fluid channels for connection to a looped solar heating system. The space between the panes may be filled with a liquid to be heated by solar radiation, or alternatively by a conduit which transports the liquid through the panel.