Total energy (in units of 10⁴¹ erg) of a 12 M_⊕ planet as a function of its luminosity. The solid red line represents a planet with f_gas = 0.1 and f_vol = 0, while the dashed blue line represents a planet with f_gas = 0.1 and f_vol = 0.7. To facilitate the comparison between the two curves, the energy of the volatile-rich planet has been multiplied by a constant factor equal to 0.39.