In this paper the economics of a small-scale humidification dehumidification desalination (HDD) unit driven by a concentrating v-trough solar thermal collector is explained. A comparative analysis using the net present value method was carried out for when the system is operated using solar energy and electricity from fossil fuels. The system could provide different amount of fresh water depending on mode of operation. It was shown that by end of year six the investment for the solar system reaches breakeven when compared to the electric system. The analysis also considers the amount of carbon savings that could be achieved and final cost of water produced per cubic meter. The factors that influence the systems economic viability are the outputs and costs of the desalination unit and solar collector systems, the cost of alternative energy source, cost of operation and maintenance, and the geographic location of the system, i.e. solar intensity, environmental temperature and humidity.