Radiative heating (or cooling) rate and radiative flux computed based on the (3D) sunA09 model. Left panel: comparison of the radiative heating (or cooling) rate computed from the 12 opacity bins shown in Fig. 1 (red plus mark) with the monochromatic solution using 250 000 wavelengths (black solid line) for the (3D) sunA09 model. The relative difference of q_rad at the cooling peak is 2.42%. Right panel: comparison between radiative flux obtained from the opacity binning method and the monochromatic solution. The relative difference of surface flux (defined as the radiative flux at log τ_Ross = −4) is 1.49%.