Bolometric luminosity light curve of SN 2006gy. The data points up to day 230 are from the absolute R magnitudes in Paper I, with no bolometric correction. The solid curve is the "shell‐shocked" photon diffusion model of Smith & McCray (2007). The two late‐time data points are lower limits to the luminosity derived from our observed ﹩K^{\prime }﹩‐band magnitudes, assuming that the SED peaks in the ﹩K^{\prime }﹩ band. Dashed lines show the expected energy deposition rate for representative masses of ⁵⁶Ni, assuming 100% efficiency of the ejecta in absorbing radioactive decay luminosity (this may be optimistic, and so the ⁵⁶Ni mass indicated by the observed luminosity may be higher). Since the late‐time IR luminosities are lower limits, we emphasize that 2.5 M_⊙ is only a lower bound for the ⁵⁶Ni mass in the radioactive decay hypothesis. Similarly, while open triangles denote KAIT and Keck/LRIS R‐band upper limits, they are not really limits to the bolometric luminosity, because the SED does not peak in the R band.