This paper presents a new design paradigm of ground heat exchanger (GHE), which takes account of uncertainty in the estimation of geothermal properties, including ground thermal conductivity and bore-hole thermal resistance from a thermal response test (TRT). Some challenges during the TRT parameter estimation process are discussed: A sensitivity analysis to a more accurate solution of the infinite line source model is introduced to identify the parameters to be estimated; a nonlinear least-square method is employed to estimate the selected parameters; and then validated by a traversing method. Afterwards, a case study is conducted to illustrate how the proposed method can be employed to a practical engineering application. The proposed uncertainty design method that provides a quantified margin of design output can be an alternative to traditional deterministic methods that simply add safety factor to expected design value. (C) 2015 Elsevier B.V. All rights reserved.