The energy potential of Irish groundwater is assessed, and its sources summarized. The two sources of energy, solar and geothermal, are outlined. The manner in which water and energy are united is described. The recovery of energy may be from the warm springs areas, from the tepid springs areas or from the high yielding cold aquifers underlying some 27% of the country. Heat pumps will be essential for their development. It is concluded that both solar and geothermal energies are of importance in Ireland; that energy extraction from the warm and tepid springs has limited potential; and that cold groundwater offers the best energy potential from Irish groundwaters.