A flat plate heating solar panel comprised of polymer materials that can withstand relatively high temperatures. The polymer materials utilized in the panel have similar thermal expansion characteristics so that different components can by connected to each other without excessive stresses and damage during temperature changes, and with major components capable of being fabricated by molding processes, including extrusion and injection molding. An expansion joint or slot is provided in the enclosure frame to allow relative movement between the header connector and the frame in order to minimize stresses when large temperature differences exist between the absorber/header and the frame, and the slot design also provides a vent to relieve excessive air pressures inside the panel at high temperatures. An electronic controller with wireless capability, powered by a small photovoltaic solar cell with energy storage by a supercapacitor or an ultracapacitor, is integrated with the panel to operate a pump to circulate a heat transfer fluid through the panel when heating capability exists and when heat is needed to increase the temperature of the substance to be heated by the panel.