A modular power supply particularly adapted for mounting to standard junction boxes in a system to provide a solid state lighting system compatible power signal. One embodiment of a modular power supply for mounting to a junction box according to the present invention includes a housing holding internal electronic components and a first extension integral to the housing for mounting to a junction box. The extension has an opening to the interior of the housing with primary wires passing from the interior of the housing through the extension. The first extension is positioned so that the power supply is capable of being mounted to the mounting surface of a junction box when the power supply is at different orientations.