In this paper, wall thermal energy loss in a cylindrical solar pond is studied using one-dimensional (1D) and two-dimensional (2D) transient models. It is seen that for a given quantity of insulation applied around the pond wall, the negative effect of sidewall loss reduces as the pond size increases. Further, the optimal insulation thickness that eradicates all wall energy loss is larger when calculated from a spatially 1D model, as opposed to when radial temperature gradients are given consideration. The 2D model reveals a larger entropy generation than that calculated by a 1D model for an imperfectly insulated pond. So, for such ponds, the present model would calculate entropy generation in a more realistic manner. It is revealed that using simpler 1D in space models to estimate solar pond’s outer wall optimum insulation thickness will not lead to any problems as far as the thermal performance is the concern. But, since such models over predict the optimum value, they would invoke more cost. So, when financial and space constraints are present, then it is advisable to design the wall insulation in solar ponds using spatially multi-dimensional heat transfer models, for which the present work could prove to be useful.