A number of stacked aquifers exists. The reason for stacking aquifers is that they may be produced simultaneously by a single well. The geothermal potential of stacked aquifers is calculated using the maps of the individual aquifers. Net thicknesses are simply added together. The weighted average permeability of the stack is calculated by using the net thickness as the weight. As a result, the net-to-gross of the stacks is equal to one. In order to calculate the uncertainty of the thickness and permeability of the stacked layers, a correlation factor of zero is assumed. This implies that the properties of the underlying aquifers vary independently from each other.
To assess the general geothermal potential, overview maps have been created for several output maps: economic potential, technical potential, power, potential recoverable heat and heat in place (see thermogis maps). This has been done by aggregating all stacked aquifers.