A modular lighting apparatus includes a replaceable bulb assembly, an adapter, and a mechanical and electrical connector assembly that removably connects the bulb assembly to the adapter for use. The bulb assembly includes a light-emitting component mounted to a body. In example embodiments the light-emitting component includes spiral-tube CFLs, low-profile transverse CFL tubes, and omni-directional LED arrays. The adapter includes a standard screw base mounted to a body that houses an electronic ballast. In this way, the bulb assembly can be removed from the adapter and replaced, while reusing the electronic ballast in the adapter. And the screw-base adapter allows the reuse of the electronic ballast in standard screw-socket household light fixtures. In addition, the reusable adapter base also may be provided with an integral photocell for light-based control of the lighting apparatus without increasing the overall height of the composite lighting apparatus.