The separate contributions to the luminosity of giant planets during the formation phase for the cold nominal accretion case. The internal luminosity L_int (top left) and the gas accretion shock luminosity L_shock (top right) is shown as a function of planetary mass for the population at 3 Myr. The bottom left panel shows the Hα luminosity obtained using the empirical L_shock−L_Hα relation from Rigliaco et al. (2012) derived for T Tauri stars. We stress that the validity of this relation in the planetary mass range is currently unknown. The observed L_Hα of HD 142527 b (Close et al. 2014) and LkCa 15 b (Sallum et al. 2015) are also shown for comparison. The bottom right panel shows the ratio of the accretion to the internal luminosity. The colors represent the planets’ gas accretion rate. The solid gray lines in the top right panel show L_shock as a function of mass for a fixed radius of 1.5 R_♃ and accretion rates of 10^-5, 10^-4, 10^-3, and 10^-2M_⊕/yr. The gray line in the bottom right panel shows a M^0.5 scaling.