For uniform thermal conditions on 3-D irregular shaped design objects, this paper reports estimation of optimal power of the panel heaters placed along the walls of a 3-D radiant furnace. Hemispherical, cylindrical, conical, and a combination of cylindrical and conical, and finally a case study of a car body model are considered as the design objects (DOs). The entire surface areas of the furnace walls and that of the DO are divided into surface elements. The surface elements of the furnace walls are made of the panel heaters. In this boundary design problem, the objective function is developed as an error function of estimated and the desired heat fluxes on the surfaces of DO. The radiative exchange among the surface elements is computed using the radiation element method by ray emission model (REM2), and the objective function is minimized using the micro-genetic algorithm (MGA). Power of the panel heaters are estimated for different sizes of the DOs. Although the panel heaters have been placed along the furnace walls, for uniform thermal conditions, for a given DO, not all are required. Having known that not all are required, to ease the control, estimations have also been shown by grouping the heaters along the furnace walls. This study provides a guideline for a priori knowing the heater setting and their corresponding power requirement in heating of 3-D irregular shaped objects. (C) 2012 Elsevier Ltd. All rights reserved.