Electrical Subpanel Installation

A subpanel is what you install when a single circuit can’t handle what you’re building, when the loads live far enough from the main panel that pulling twelve separate branch runs is silly, or when you want the breakers close to the equipment they serve. Wave Electric installs subpanels for garages, workshops, additions, ADUs, pool equipment pads, and detached buildings across Baldwin County. Jimmy is a licensed Alabama electrician (license #02617), and every subpanel is sized right, fed right, grounded right, and inspected.

Subpanels are one of the areas where cutting corners on the install shows up years later as either a fire risk or a code violation that comes up during a home sale. The most common problem Jimmy finds on existing subpanels: neutral and ground bonded together at the subpanel (they shouldn’t be, downstream of the main), undersized feeders that were fine for the original load but are now overloaded, missing grounding electrodes at detached buildings, and disconnects that aren’t rated for the ampacity they’re carrying.

When a subpanel makes sense

• You’re finishing a garage into a workshop and need multiple 20A circuits for tools, a couple of dedicated 240V circuits for a table saw or dust collector, and lighting
• You’re building an addition (primary suite, second-floor space, sunroom) and pulling every branch circuit back to the main panel would mean fishing wire through the whole house
• You’re adding an ADU, mother-in-law suite, or guest house on the property, and it needs its own dedicated panel
• You have a detached shop, barn, or pole building that needs power, either fed underground or overhead
• Your pool equipment pad has grown (pump, heater, salt system, lift, spa) and the current setup is a spider’s nest of extension cords
• You have a home office or media room where a subpanel gives you clean circuit isolation and headroom for future equipment

When a subpanel isn’t the right answer

A subpanel only helps if your main service panel can actually feed it. If your main is a 100-amp panel that’s already carrying most of the load your home draws, adding a subpanel doesn’t magically create capacity. It just moves where the breakers live while the same total current still flows through the main. In that case, the honest answer is a service upgrade first (usually to 200 amps), and then the subpanel installed off the upgraded service.

Jimmy runs a load calculation on the main before recommending a subpanel. That means adding up the connected loads, applying the demand factors the NEC lets you use for residential calculations, comparing that against the main service size, and being honest about whether there’s real headroom or whether a service upgrade is the actual first step. Sometimes the answer is “you need both.” Sometimes it’s “you’re closer to full than you think, and adding this addition without an upgrade is going to trip your main every summer when the AC and dryer are running together.”

Feeder sizing

Feeder sizing is where subpanel installs most often go sideways in DIY or unlicensed work. The feeder is the set of conductors that runs from the main panel to the subpanel, and it has to be sized for both the ampacity of the subpanel and the distance of the run. Voltage drop matters: a feeder that’s technically legal for the amperage but too small for the distance will drop enough voltage under load that motors run hot and lights dim when the AC kicks on.

Common feeder sizes Jimmy pulls for residential subpanels:

• 60-amp subpanel, short run: #6 copper or #4 aluminum with a #10 copper ground
• 100-amp subpanel, moderate run: #3 copper or #1 aluminum with a #8 copper ground
• 100-amp subpanel to detached building, 100+ feet: #1 or #1/0 aluminum with a #6 copper ground and a separate grounding electrode at the building
• 125-amp subpanel for a shop with 240V equipment: #2 copper or #1/0 aluminum with a #6 ground
• 200-amp subpanel for an ADU: #4/0 aluminum SER cable or equivalent

Every job gets calculated for its specific distance and load. Wave Electric doesn’t guess.

Detached buildings: the parts most people get wrong

Feeding a subpanel to a detached building (a shop, a pole barn, a garage across the driveway, a guest house) has some specific NEC requirements that don’t apply to a subpanel inside the same building as the main panel:

Four-wire feeder. The feeder from the main to the detached building must include a separate equipment grounding conductor. Old three-wire installs (two hots and a neutral, no separate ground) are no longer code-compliant for new work.

Separate grounding electrode at the building. The detached building needs its own grounding electrode system (typically two ground rods, or a Ufer ground if the slab has accessible rebar). This is bonded to the ground bar in the subpanel.

Neutral and ground kept separate. In the subpanel at the detached building, the neutral bar must be isolated from the ground bar. The bonding screw or strap that ties them together in a main panel does not belong in a subpanel.

Disconnect at the building. If the subpanel is inside the detached building, the main breaker on that subpanel serves as the disconnect. If the subpanel doesn’t have a main, you need a separate service disconnect at the building’s exterior.

All of this is what a licensed electrician handles automatically and what unlicensed work almost always misses.

What the process looks like

Jimmy comes out for a free quote and starts with the load. What are you feeding? A 5-hp dust collector and a welder, or LED lights and a couple of outlets? Then the distance. Then the path, attic, crawl, buried conduit, or overhead. Then the main panel: is there room, is there capacity, does the service need an upgrade first? You get a written quote with the panel size, feeder size, run path, and total cost, plus a timeline.

Once you sign off, Wave Electric pulls the permit, coordinates any brief power interruption on your main, runs the feeder in the appropriate wire type and conduit for the environment, mounts the new subpanel, lands the feeder correctly (neutral isolated from ground in the subpanel, grounding electrode installed if the panel is at a detached building), and either builds out the branch circuits or leaves the subpanel ready for future circuits depending on your scope. The inspector comes out, everything gets signed off, and you have a properly permitted subpanel with documentation.

Most residential subpanel installs are a one-day job. Detached-building installs with a trench for underground feeder run to two or three days depending on the length of the trench and whether we’re hitting sandy soil, red clay, or the roots of every live oak between here and the shop.

Commercial and industrial subpanels

For commercial buildings and industrial facilities across Baldwin County, subpanel installation looks similar but scales up. Larger feeders, three-phase in most cases, sub-fed distribution to equipment areas, and coordination with existing overcurrent protection so a fault at one machine trips its own subpanel breaker without knocking out the whole building. Wave Electric handles commercial and industrial subpanel work as part of larger buildouts, tenant fit-outs, and equipment additions.

Call Wave Electric

Wave Electric installs subpanels across Baldwin County: Fairhope, Daphne, Spanish Fort, Foley, Gulf Shores, Orange Beach, Robertsdale, Bay Minette, and Loxley. Call Jimmy at 251-656-4601 or request a free quote. Licensed, insured, permitted, and inspected. Done right the first time, sized for what you’re actually running, and set up so the next electrician who opens the panel finds it clean.