Junction box installation costs $100 to $300 for parts and labor, depending on the installation location, accessibility, and the electrical box size, material, and indoor or outdoor rating. Plastic junction boxes for indoor wiring cost 50% to 80% less than metal boxes but aren't as durable. If you're planning any electrical work, one of the small but important items on your list will be the junction box. At first. Cable joint kits provide comprehensive solutions for connecting and repairing electrical cables in various installations. High-quality terminal boxes from trusted suppliers with Fast Delivery.