Office Build-Out Electrical in San Antonio: A Planning Guide for Tenants and GCs

Office build-out electrical is the part of a lease that most tenants never see and most schedules depend on. A suite can go from a bare shell to a working office in a few weeks, but only if the power, the lighting and the data are planned before the walls close. This guide walks through how an office build-out is wired in San Antonio, in the order the work actually happens, so a tenant, a property manager or a general contractor can plan around it.

Start with the furniture plan, not the floor plan

A floor plan shows walls. A furniture plan shows where people sit, where the printers go, where the break room appliances land and how the conference rooms will be used. The electrical layout follows the furniture plan. If the desks move after rough-in, the outlets, floor boxes and data drops move with them, and moving them after the drywall is up costs time and money.

The questions to answer early are simple. How many workstations, and do they sit against walls or in open rows? Do any rows need power from the floor or from a ceiling feed into the furniture? Where does the copier sit? Is there a server or network closet, and what does it hold? What goes in the break room: a refrigerator, a microwave, a coffee machine, a dishwasher? Each answer becomes a circuit or a device on the plan.

Can the existing service carry the new layout?

Most office suites in San Antonio come with a panel already in place, fed from the building's main service. The first electrical question in any build-out is whether that panel, and the feeder serving it, can carry what the tenant is adding. The answer comes from a load calculation under NEC Article 220, which adds up lighting, receptacles, equipment and HVAC and compares the total with what the panel and feeder are rated for.

If the numbers work, the job uses the existing panel and adds circuits. If they do not, the panel may need to be replaced or a second panel added, and sometimes the feeder from the building's main distribution has to be upsized. That is work the landlord usually has to approve, so it is far better to find out during pricing than during rough-in.

When a suite needs a larger panel or a new feeder, the work is the same trade as a home panel upgrade at a larger scale. Our panel upgrade service explains what a panel change involves and why the load calculation comes first.

Workstation power and the network closet

Open office rows are usually fed through the furniture system, from a wall, a floor box or a power pole from the ceiling. The number of workstations on each circuit depends on what each desk runs. A desk with a laptop, two monitors and a phone charger draws far less than one with a space heater under it, and the plan should be honest about which kind of office it is.

The network closet deserves its own circuits. Switches, the router, the phone system and any small server should be on dedicated circuits that do not share a breaker with the break room. Many tenants also want a receptacle for a battery backup unit at the rack. If the closet will hold equipment that runs warm, its cooling needs power too. Settling this early keeps the data contractor and the electrician from working against each other.

Break rooms, conference rooms and the small details

Break rooms collect the loads that trip breakers: a refrigerator, a microwave, a coffee maker and sometimes a dishwasher and an ice machine. Each heavy appliance should have its own circuit, and receptacles near the sink need GFCI protection. Under NEC 210.8(B), commercial spaces also need GFCI protection for receptacles in break rooms and other areas the code lists, so the protection is planned in rather than added after an inspector asks.

Conference rooms usually need power and data at the table, a feed for a wall display, and sometimes a dedicated circuit for audio and video equipment. Reception desks, badge readers, door strikes and wall clocks each need a feed in the right spot. None of these is hard, but every one forgotten during rough-in becomes a patch in a finished wall.

• One circuit per heavy break room appliance, with GFCI where the code requires it.
• Table power and data in conference rooms, plus a feed behind the display.
• Dedicated circuits for the network closet and any small server.
• Power for access control, door hardware and the reception desk.
• Spare capacity in the panel for the next change the tenant makes.

Lighting and lighting controls

Office lighting in a build-out is usually LED troffers or linear fixtures in the ceiling grid, with downlights in corridors and decorative fixtures at reception. The energy code adopted in Texas sets limits on how much lighting power a space can use and calls for controls: occupancy or vacancy sensors in offices and conference rooms, the ability to reduce light levels, and daylight controls near windows in many spaces. The controls are part of the permit drawings and the inspector checks them.

Exit signs and emergency lighting are part of the build-out as well. New walls change the path people take to the exits, so emergency lighting has to cover the new corridors and rooms, and exit signs have to be visible from the new layout.

Our emergency lighting and exit sign page covers what those fixtures need after they are installed, including the monthly and annual tests.

Permits and the inspection sequence

Inside the city limits, commercial electrical permits are issued through the City of San Antonio Development Services Department, and the city adopted the 2023 National Electrical Code effective May 1, 2025. Suburban cities such as Boerne, Schertz and New Braunfels run their own permit offices. A build-out of any size typically needs drawings with the permit, and the electrical contractor pulls the electrical permit and meets the inspector.

The inspections come in order. Rough-in is inspected before insulation and drywall cover the wiring in the walls. An above-ceiling inspection checks the work in the ceiling before the tiles go in. The final inspection checks devices, fixtures, panel labeling and working space in front of the panel, which NEC 110.26 requires to stay clear. Each inspection has to pass before the next trade can close up, so the electrical schedule sits right in the middle of the general contractor's schedule.

We wrote a separate walk through the whole sequence for any suite in our guide to tenant build-out electrical, and our tenant build-out service page explains how we run those jobs with a GC.

Working in an occupied building

Many office build-outs happen in buildings where the neighbors are open for business. Tying new circuits into a shared panel, or shutting down a feeder, can affect other tenants. Those outages have to be planned with the property manager, announced in advance and kept short, which often means doing them early in the morning, in the evening or on a weekend. We schedule that work after hours when the building needs it.

What a clear office build-out bid includes

A clear electrical bid for an office build-out names the scope room by room, the panel and feeder work, the fixtures and who supplies them, the lighting controls, the permit and the inspections. It says what is excluded, such as data cabling if another contractor is doing it. It also says how a change will be priced. At Wattsmith every change gets a written price and your approval before the work is done.

If your office is a medical or dental suite, the rules are stricter, and our guide to medical and dental office electrical covers the differences. For everything else we do for businesses, see our commercial electrical services.