A sub-panel is the right answer when your main panel is full, the new circuits are far from the load center, or you want to isolate a high-load area like a pool, hot tub, or detached garage. We install 60A, 100A, and 125A sub-panels with permit, inspection, and the correct grounding for attached or detached buildings.
A sub-panel is a smaller load center fed from your main service panel. It distributes power to a specific area — a detached garage, an ADU, a workshop, a pool equipment pad, a hot tub disconnect — without you having to run individual circuits all the way back to the main panel. Three common reasons we install them in Columbia:
The main panel is full. If your main panel has no available breaker slots, you can install a sub-panel anywhere on the property and have plenty of expansion room. Common in older Forest Acres, Shandon, and West Columbia homes built before 200A service became standard.
The new work is far from the main. A detached garage at the back of a Lake Murray property, an ADU over a Cobblestone Park guest house, a workshop on a Spring Valley lot — each is more efficient to feed with a single larger feeder to a sub-panel than to run 6-10 individual circuits 100+ feet underground.
You want isolation. Pool equipment, hot tubs, and EV charging benefit from being on their own sub-panel because you can shut off everything in that zone with one breaker, the GFCI requirements are concentrated in one box, and future expansion (adding a pool heater, a second EV charger, a deck heater) is easier.
100A typical for a garage with EV charging, tools, and HVAC. Underground feeder in PVC conduit at NEC-required depth. Two ground rods required at the detached structure.
100A or 125A for a full ADU with kitchen, HVAC, and water heater. Compliant with the City of Columbia's ADU permit process. Coordinated with the GC and the AHJ.
60A or 100A for woodworking shops, mechanic shops, and hobby spaces. Sized for compressor, welder, dust collection, and 240V tools running simultaneously.
NEC 680-compliant pool sub-panel housing GFCI breakers for pump, salt cell, heater, lighting. Equipotential bonding grid integrated. Common around Lake Murray and Saluda River Club.
Code-required disconnect for hot tubs doubles as a mini sub-panel for outdoor circuits. GFCI breaker integrated. Bonded to the equipotential plane around the tub.
Permit pulled with Richland or Lexington County. Inspection scheduled and met. Dominion coordination if a service-side change is needed. Carrier-ready documentation provided.
We install sub-panels across the Midlands. The biggest concentrations are Lake Murray and Saluda River Club (pool and hot tub installs), older Columbia and Forest Acres (full main panels), and newer Cobblestone Park and Spring Valley (ADUs and workshops).
Three common triggers: (1) the main panel is full and you need 4+ new circuits, (2) the load center is far from where the new work is going (a detached garage, workshop, or ADU), or (3) you want to isolate a high-load area (pool equipment, hot tub, EV charging) on its own subpanel for easier shutoff. We do a load calculation as part of the quote — if the main has space and capacity for the new circuits, we'll tell you straight that a sub-panel isn't needed.
Most detached garages and workshops in Columbia get a 60A or 100A sub-panel. 60A is enough for lighting, outlets, an air compressor, and a 240V welder used occasionally. 100A is what you need for an EV charger, a heat pump or mini-split, multiple 240V tools, and future expansion. For ADUs (accessory dwelling units with a full kitchen and HVAC), 100A is the minimum and 125A is increasingly common.
A 60A sub-panel in an attached garage with a short feeder run is typically $1,200-$1,800 installed. A 100A sub-panel feeding a detached garage or workshop runs $1,800-$3,500, depending on the trench distance (a 100-ft underground run adds materials and labor) and whether trenching crosses landscaping or paved areas. Permit fees and inspection are included.
Detached buildings (separate from the main house) require their own grounding electrode system at the sub-panel — usually two 8-foot ground rods. Attached buildings or sub-panels inside the same structure as the main panel don't need a separate ground rod — they share the main panel's grounding. The neutral and ground are kept isolated at the sub-panel (only bonded together at the main panel). The inspector verifies this on every install.
Yes — and it's often the cleanest install for pool equipment. The pool sub-panel houses the GFCI breakers for the pool pump, salt cell, heater (if electric), and pool lighting. NEC 680 governs pool electrical work; bonding requirements are extensive. We install pool sub-panels regularly and pair them with the proper equipotential bonding grid. Lake Murray and Cobblestone Park pool installs are common projects.
Not usually. A typical 40-50A EV charger circuit goes directly from the main panel. Sub-panels make sense when (1) the garage is detached and far from the main, (2) you want EV charging + other 240V loads in the same area (welder, tools), or (3) the main panel is already full. For Tesla Wall Connector and Universal Wall Connector installs, see our dedicated page.
We'll size the sub-panel correctly the first time.