Three electrical injection schemes based on recently demonstrated electrically pumped photonic crystal nanolasers have been numerically investigated: 1) a vertical p-i-n junction through a post structure; 2) a lateral p-i-n junction with a homostructure; and 3) a lateral p-i-n junction with a buried heterostructure. Self-consistent laser-diode simulations reveal that the lateral injection scheme with a buried heterostructure achieves the best lasing characteristics at a low current, whereas the vertical injection scheme performs better at a higher current for the chosen geometries. For this analysis, the properties of different schemes, i.e., electrical resistance, threshold voltage, threshold current, and internal efficiency as energy requirements for optical interconnects are compared and the physics behind the differences is discussed.