Heat extraction from the Non-Convective Zone (NCZ) or gradient layer and Lower Convective Zone (LCZ) of the solar pond has been investigated through one-dimensional finite difference transient model. Instantaneous efficiency of the solar pond is introduced and defined in this paper. The solar pond considered in the present study is assumed to have an in-pond heat exchanger for heat extraction. The rate of heat transfer is controlled by the mass flux of heat transfer fluid in this model. As in reality mass flux of heat transfer fluid is the simplest and most practical way to control the rate of heat extraction. In this model for an ideal situation it is assumed that the heat transfer fluid is initially at the local daily average ambient temperature and the in-pond heat exchanger has heat transfer effectiveness equal to unity. With these assumptions the model can predict the thermal performance of the solar pond with maximum heat extraction for a desired mass flux of the heat transfer fluid. This paper presents the comparison of the transient thermal performance of solar pond with heat extraction from LCZ alone and that with combined heat extraction from LCZ and NCZ. It is shown how the efficiency of the solar pond increases when heat is extracted from both NCZ and LCZ. The main objective of this study is to offer a simple method to predict transient thermal performance of a solar pond with heat extraction from NCZ and to estimate the mass flux of heat transfer fluid used in an in-pond heat exchanger for heat extraction from different layers of solar pond. (C) 2013 Elsevier Ltd. All rights reserved.