If your main panel is full, or you’re planning an addition, a workshop, or an EV charger that needs more circuit capacity than you have room for, a subpanel is often the answer. Here’s how to tell if you need one and what’s involved in adding one.
Signs You Might Need a Subpanel
Your main panel is out of open slots. If every breaker space is full and you need to add circuits, a subpanel extends your capacity without replacing your entire main panel.
You’re finishing a garage, workshop, or detached structure. Detached spaces like garages, workshops, or ADUs typically need their own subpanel fed from the main panel, both for convenience and to meet code requirements for separate structures.
You’re adding a major new load. EV chargers, hot tubs, workshop equipment, and similar additions often warrant their own dedicated subpanel rather than squeezing another breaker into an already-tight main panel.
How Subpanel Sizing Works
Subpanels are sized based on the actual loads they’ll serve and how much capacity your main panel and service can spare. This isn’t a guess-and-check process — it requires a load calculation to confirm your main service can support the added subpanel without being overloaded, which sometimes means a main panel or service upgrade needs to happen first.
Why This Is Licensed Electrician Work
Installing a subpanel means running a properly sized feeder from your main panel, correctly bonding and grounding the new panel, and making sure the whole system is balanced and within code. Done wrong, an improperly grounded or oversized subpanel is a real fire and shock hazard. In Washington, subpanel installations require a licensed electrician and a permit with inspection.
What to Expect From a Professional Installation
Your electrician will evaluate your main panel’s available capacity, size the subpanel and feeder for your actual planned loads, run the wiring, install and properly ground the new panel, and have the work inspected before it’s energized.
Thinking About a Subpanel?
Mauro Electric Inc. has installed subpanels throughout Bothell and the greater Seattle area since 1998. Contact us to talk through your project, or call 360-653-5300.
