This paper introduces four new parameters, namely energetic renewability ratio, exergetic renewability ratio, energetic reinjection ratio, and exergetic reinjection ratio for geothermal district energy systems. These parameters are applied to Edremit Geothermal District Heating System (GDHS) in Balikesir, Turkey for daily, monthly and yearly assessments and their variations are studied. In addition, the actual data are regressed to obtain some applied correlations for practical use. Some results follow: (i) Both energetic and exergetic renewability ratios decrease with decreasing temperature in heating season and increasing temperature in the summer. (ii) Both energetic and exergetic reinjection ratios increase with decreasing temperature for heating season and increase with increasing temperature for summer season. (C) 2008 Elsevier Ltd. All rights reserved.