This paper describes the development of a design tool for the calculation of the thermal energy potential of a so-called asphalt collector. Two types of numerical models have been developed and validated against experimental results from a full-scale test-site. The validation showed to be a tedious procedure due to the complexity of the full-scale testing of this type of systems. Nevertheless, the models are found to be applicable for performing design studies with. Example results presented in the paper indicate that the thermal energy potential of an asphalt collector is lower than that of a normal solar hot water system. The quality of the energy is also less. However, further advantages of the use of an asphalt collector are found in the reduced maintenance of the road and the avoidance of slippery roads in winter time. The latter is also an example of the heat exchanger capabilities of the asphalt collector.