With a hot plate and a spherical mirror, a highly efficient crucible heating furnace was theoretically calculated and constructed. The upper part of the crucible provides free access to the melt, as is needed in the Czochralski crystal growth technique. For the design, the heat radiation flow between the hot plate, a cylindrical crucible, and the enclosing ellipsoidal mirror was computed. The calculated temperature profiles on the crucible, for different values of the crucible diameter and the eccentricity of the ellipsoid are shown and a comparison is made with the constructed oven. Using a cylindrical crucible (od=5 cm, height=5 cm), the power consumption is 720 W during the growth of NaCl (≈800 °C).