A mathematical model of the behaviour of a geothermal-energy source, based on the theoretical water well of different quality parameters has been presented. Heat energy magnification produced by the well by increasing the stream of pumping water is analysed. Optimisation analyses are conducted assuming different types of source: constant or dynamic parameters. The technical optimisation model maximises the net power of the source, which is the difference between the heat source power and the power of pumping. The optimisation model maximises the value of heat energy produced by the source minus the value of the electrical energy used for pumping. The technical and economic optimisation gives different results because the unit cost of heat energy is lower than that of electrical energy. (C) 2003 Published by Elsevier Science Ltd.