At early stages of geothermal development, resources capacity can be quantified using Volumetric Stored Heat method. The method estimates potential generated amount of power for a period (e.g. 30 years) based on recoverable energy stored in the reservoir and surface conversion efficiency. Extractable stored heat in the reservoir is estimated from thermal energy in-the rock and the fluid in specified reservoir volume, reservoir temperature, and reference or final temperature. The method incorporates Monte Carlo Simulation to be able to quantify the uncertainty of estimates of the geothermal resources and therefore better understand the risks and opportunities associated with resources capacity.