Junction box costs range from low‑price indoor models ($10‑$60) to weatherproof units ($70‑$450), with installation averaging $100‑$300 depending on location and materials. If you're planning any electrical work, one of the small but important items on your list will be the junction box. Plastic junction boxes for indoor wiring cost 50% to 80% less than metal boxes but aren't as durable. The total often includes the panel enclosure, breakers, wiring, and professional. In May 2026 the estimated national average cost to Install an Electrical Service Panel starts at $1,305 - $1,581 per panel. Costs vary based on amp rating, construction materials, socket type, overhead vs.