A system for mounting a solar panel(s) on a building may include a panel mounting bracket(s) including a base to be positioned on the building, a vertical extension having a proximal end coupled to the base and a distal end vertically spaced apart from the base, and a first lateral extension carried on an exterior surface of the vertical extension. An extension device for the at least one panel mounting bracket may include a first portion, a second portion carried by the first portion to be connected with the at least one solar panel, a second lateral extension carried by the second portion to be vertically aligned with the first lateral extension, and a screw including a head carried by the second portion to set the extension device relative to the base.