A theoretical analysis on a novel “Invisible Solar Panel” has been carried out to evaluate its thermal performance. The sandwich collector is made of roof tiles - polyethylene exchanger ready loop - aluminium –insulation, all the system could be easily integrated as part of the roof structure. The roof tiles (PV, slate, clay or concrete) was used to maximise the solar energy absorption. During hot summer days, the backing aluminium/tiles may reach temperature over 45°C, and could provide heat source for Domestic Hot Water (DHW) or heat power for regeneration power in a Liquid Desiccant Air Conditioning. Based on energy balance of each parts of the sandwich collector, mathematical models have been developed to evaluate the thermal performance of the “Invisible Solar Panel”. The energy performance of the system has been investigated under the climatic conditions of the City of Nottingham, UK. The simulation results indicate that the average monthly thermal efficiency was about 8%, and the heat generated was about 120Wh for approximately 3sqm of the “Invisible Solar Panel”.