In this study, an experimental and theoretical investigation of temperature distributions in an insulated solar pond, particularly during daytimes and nighttimes, is presented. Several temperature sensors connected to a data acquisition are placed vertically inside and the bottom of the pond and also horizontally and vertically in the insulated side walls, and used to measure temperature changes with time and position. In addition, we model the solar pond to compute theoretical temperature distributions and compare with the experimental measurements, and hence a good agreement is found between experimental and theoretical temperature profiles. There is a large amount of heat losses between daytimes and nighttimes, depending upon the temperature difference, and these present a significant potential for energy savings and storage. During the months of January, May and August, it is found that the total beat losses from the inner surface of the pond and its bottom and side walls, as a function of temperature difference, are determined to account for 227.76 MJ (e.g., 84.94% from the inner surface, 3.93% from the bottom and 11.13% from the side walls, respectively). (c) 2005 Elsevier Ltd. All rights reserved.