Abstract: District energy (DE) systems provide an important means of mitigating greenhouse gas (GHG) emissions and the significant related concerns associated with global climate change. DE systems can use fossil fuel, renewable energy and waste heat as energy sources, and facilitate intelligent integration of energy systems. In this paper, solar thermal and geothermal energy are compared as energy sources for a district energy system which serves a community including commercial and educational buildings. The DE system is assessed for the considered energy resources in two main ways, by considering CO₂ emissions and economic aspects. The results obtained for the solar and geothermal energy sources are compared to detect trends. The results indicate that solar thermal energy is the most advantageous energy technology for a DE system from an environmental perspective, while geothermal energy is more beneficial from a financial point of view. An examination of the cost distribution for the technologies shows that when solar thermal energy is the main energy supply for a DE system, the system exhibits the highest loan payments and the lowest fuel costs (FCs) and insurance and maintenance (I&M) payments. With geothermal systems, loan payments are lower while the total cost over the life of the technology is higher for the DE system. Using solar thermal and geothermal technologies as the energy supply for a DE system also yields environmental benefits which can lead to financial advantages through such instruments as tax breaks. The research reported here is intended to allow energy technology suppliers to work with communities while accounting appropriately for economic issues and CO₂ emissions associated with these energy technologies.