Key takeaways
- A warehouse electrician lays out the power to the floor plan: the racking, the dock, the charging area and the equipment, not just the empty building.
- Many San Antonio warehouses have 480 volt three-phase service, with a transformer stepping down to 208Y/120 volts for receptacles, offices and small loads.
- High bay LED lighting has to put light at the rack faces and the aisles. A layout drawn for an empty floor can leave the aisles dark once racking goes up.
- Lift truck chargers, dock levelers, door operators and conveyors each need a circuit and a disconnect in the right place before the equipment arrives.
A warehouse electrician works in a building that looks simple and is not. The shell is a large open space, but the work inside depends on a plan that changes as the tenant moves in: racking goes up, aisles form, the dock fills with equipment and lift trucks need a place to charge. San Antonio's distribution and light industrial buildings along the major highways are built for that kind of change. This guide explains what electrical work a warehouse needs, in the order it is usually planned, and what an owner or tenant should settle first.
Understand the service the building has
Most larger warehouses are served at 480 volts, three-phase, because motors, heaters, chargers and high bay lighting run efficiently at that voltage. Receptacles, office areas and small equipment run at 208Y/120 volts, supplied by a step-down transformer inside the building. Smaller flex and light industrial spaces may be served at 208Y/120 volts only. Knowing which voltages are available, and how much capacity is left on each, is the first step in any warehouse electrical project.
The service and its distribution are covered by NEC Article 230 for the service itself, and the equipment beyond it by the articles for feeders, transformers and motors. In practice the question is simpler: can the existing switchgear, panels and transformer carry what the tenant is bringing? A load calculation answers it, and if the answer is no, a larger transformer, a new panel or a service upgrade coordinated with the utility may be part of the job. In most of the San Antonio area that utility is CPS Energy.
Larger services and new panels follow the same logic as our panel upgrade service, at the scale of a three-phase commercial building.
High bay lighting that works with the racking
Warehouse lighting is almost always high bay LED fixtures now, often with built-in occupancy sensors. The common mistake is laying out the fixtures for an empty floor. Once racking goes up, the light has to reach down the aisles and onto the rack faces where people read labels and pick product. A layout drawn to the racking plan puts rows of fixtures over the aisles rather than over the tops of the racks.
The energy code adopted in Texas sets a lighting power allowance for warehouses and calls for automatic controls, so aisles that sit empty most of the day can dim or switch off on their own. Occupancy sensing in the aisles also saves energy without anyone touching a switch. Emergency lighting and exit signs have to cover the paths to the exits, which change when racking and walls go in.
If the building already has old metal halide or fluorescent high bays, our LED lighting retrofit page explains how a retrofit is planned and done while the warehouse keeps working.
Dock doors, levelers and door operators
The dock is the busiest electrical area in a warehouse. Each door may have a powered overhead door operator, a hydraulic dock leveler, a vehicle restraint, a dock light and a set of signal lights, and sometimes a fan. Each piece needs power at the door, usually with a disconnect, and the controls often have to be wired together so a leveler and a restraint work in the right order. The equipment supplier's sheets set the voltage and the circuit size.
- Overhead door operators, usually three-phase at the larger doors.
- Hydraulic dock levelers and vehicle restraints with their control wiring.
- Dock lights and interior and exterior signal lights.
- Receptacles at the dock for tools and portable equipment.
- Exterior lighting over the truck court and the doors.
Lift truck charging
Electric lift trucks need a charging area, and the chargers are usually the largest single load a warehouse tenant adds. Battery chargers for traditional lead acid batteries and the newer lithium ion chargers each have their own requirements, and the supplier's sheets name the voltage, often 480 volts three-phase, and the circuit size. A charging area with several chargers needs a feeder and a panel sized for all of them running at once, because they usually do, overnight.
Lead acid battery charging areas also have ventilation and layout requirements beyond the electrical work, and the fire marshal or building official may look at them. Lithium ion systems avoid some of those requirements. Either way, the charging area belongs on the plan early, with the number of trucks the tenant expects to run, so the feeder is sized once.
If the fleet includes electric trucks that charge at the building, that is a separate system covered on our EV and fleet charging page.
Power to the floor: racking, conveyors and equipment
Equipment in a warehouse rarely stands next to a wall. Conveyors, packing stations, stretch wrappers, balers and compactors land in the middle of the floor, and their power comes down from the structure or up through the slab. Busway run along the ceiling lets equipment be added or moved with plug-in units rather than new conduit runs. Cord drops from the ceiling serve packing stations. Each piece of motor-driven equipment needs a disconnect where the code requires it, within sight of the motor.
Clearances matter too. Panels and disconnects need the working space in front of them that NEC 110.26 requires, and in a warehouse that space is often lost to stacked pallets. Marking the floor in front of electrical equipment and keeping racking out of it avoids a problem at inspection and during the next repair.
Plan for growth while the conduit is going in. A warehouse tenant rarely stays with the first equipment list, and adding a conveyor line or more chargers a year later is much easier if the panel has spare spaces and the feeder has spare capacity. Empty conduits from the electrical room to the likely equipment areas cost little during the original work and save a great deal of cutting and patching later. Labeling every panel, disconnect and circuit to match the final drawings helps the next electrician who works in the building find what feeds what without shutting down the wrong load.
Offices, break rooms and the rest of the building
Most warehouses include an office area, restrooms, a break room and sometimes a mezzanine. Those areas are wired like an ordinary office at 208Y/120 volts: lighting, receptacles, a network closet, and GFCI protection where NEC 210.8(B) requires it in commercial spaces. Exterior lighting around the truck court and the parking area, and power for gates and cameras, round out the job.
The office portion follows the same plan we describe in our office build-out electrical guide.
Permits, schedule and keeping the building running
Inside San Antonio, commercial electrical permits go through the Development Services Department under the 2023 National Electrical Code, which the city adopted effective May 1, 2025. Suburban cities and unincorporated parts of the county have their own rules, and some industrial parks sit outside the city limits. The electrical contractor pulls the electrical permit and meets the inspector.
Work in an operating warehouse is planned around shipping. Shutdowns for tie-ins happen on a weekend or a slow shift, and lighting work over active aisles is done in sections. Once the building is running, a maintenance agreement keeps an eye on the loaded equipment, the chargers and the dock, where loose connections and worn parts show up first.
See our maintenance agreements for scheduled service, and our commercial electrical services for everything else we do for businesses.