In conventional analysis of projects, economists traditionally apply a discount rate to determine the present value of a future asset, say an income stream from geothermal production. When this is done for the relatively long time periods of interest in sustainability, the present value of future geothermal production becomes very small. According to this method of valuing a future asset, there is little economic incentive for a geothermal developer to extract energy from a resource in a sustainable way. Direct-use values for energy resources are fairly straightforward, and are given by current economic analysis if these analyses include external costs of using the resource. Indirect-use values consist mainly of values given by ecologists, and are important but may be difficult to quantify for energy resources.
Existence values relate to all other valuations of the natural asset, such as scenic beauty.
The total economic value offers a comprehensive framework within which to value natural assets such as geothermal energy resources. If a system of analysis based on the TEV were implemented, it would be a significant departure from traditional economic analyses of geothermal resources and contribute to a more sustainable rate of production from them. However, much remains to be learned and accepted by governments and markets before modified systems of national accounts and project analysis will be adopted that take the sustainability of the natural environment into full consideration. Thus, it may not be necessary that any specific geothermal field be exploited in a sustainable fashion. Perhaps we should direct our geothermal sustainability studies toward reaching and then sustaining a certain overall level of geothermal production at a national or regional level, both for electrical power generation and direct-heat applications, for a certain period, say 300 years, by bringing new geothermal systems on line as others are depleted.