Subpanel
A smaller breaker box fed from your main panel that adds circuits for a garage, addition, or workshop.
A subpanel (or sub-panelboard) is a secondary breaker box wired off your [main panel](/glossary/main-breaker) by a single feeder circuit. It doesn't add capacity to your home — it borrows from the main panel's existing amperage — but it gives you a local cluster of breakers where you need them: a detached garage, a finished basement, an addition, or a workshop. A subpanel is often the cheaper fix when your main [service panel](/glossary/service-panel) is simply out of open slots rather than out of capacity. A load calculation still decides whether your service can spare the amps. See [the cost to replace or upgrade an electrical panel](/guides/cost-to-replace-electrical-panel).