Commercial Electrical Service Upgrade: When the Building Outgrows Its Power

A commercial electrical service upgrade becomes necessary when a building asks for more power than its service was built to deliver. It rarely happens all at once. A restaurant adds a second line of equipment, an office fills with servers and new HVAC, a warehouse adds lift truck chargers, or a new tenant arrives with loads the last one never had. At some point, the service, the main equipment and the utility transformer reach their limit. This guide covers how to tell, how the need is confirmed, and how the work is planned so the business keeps running.

If your question is mainly about three-phase power and replacing panels, our post on three-phase service and commercial panel upgrades covers that side. This one is about the service as a whole and the steps to grow it.

Signs the service is too small

• The main breaker or feeder breakers trip at busy times of day.
• Panels and the main switchgear run warm, or show discoloration at connections.
• There is no space left for new breakers, and circuits have been doubled up.
• Lights dim when large equipment starts.
• A planned addition, such as new equipment or EV chargers, will add load the building has never carried.

Any one of these is worth a look by a licensed electrician. Heat and discoloration in particular are signs of a connection or a conductor working beyond its limit, and they should not wait.

Confirming it with a load calculation

Whether a service is large enough is not a judgment call. The National Electrical Code sets the method in Article 220, which adds up the lighting, receptacles, motors, HVAC and other equipment, applies the factors the code allows, and compares the result with the rating of the service and its equipment. For an existing building, actual demand data from the utility or measurements taken over a period can also be used to show how much capacity is really being used.

The calculation is done for the building as it will be, with the planned additions included. That answer tells you whether you can add what you want on the existing service, whether part of the load can move to a new panel fed from existing capacity, or whether the service itself has to grow.

The utility side, with CPS Energy

A service upgrade has two halves. The customer side includes the service entrance conductors, the meter equipment, the main disconnect and the distribution inside the building. The utility side includes the transformer and the utility's connection to the building. In most of the San Antonio area that utility is CPS Energy. The utility reviews the request, decides what it needs to provide, and schedules its own work. Its timeline is often the longest single part of the project, so the request should go in early.

The electrical contractor prepares the information the utility needs, coordinates the meter and service equipment requirements, and lines up the customer side work so it is ready when the utility is.

Options short of a full upgrade

A load calculation sometimes shows that the service is close to its limit but not past it, or that the problem is how the load is spread rather than how much there is. In those cases there may be options that cost less than a full service upgrade. Loads can be rebalanced across the phases so no single phase is overworked. A new panel can be fed from capacity that is available in the existing distribution. Large loads can be managed so they do not all run at their peak at the same time.

These options have limits. They do not create capacity that is not there, and they only make sense when the calculation supports them with room to spare. When a building is clearly past its limit, or when a large planned addition would put it there, the service upgrade is the honest answer and the other options only delay it.

Equipment and lead times

Larger service equipment, switchgear and transformers can have long lead times. Ordering early, as soon as the scope is settled, keeps the equipment from becoming the reason a project sits. The bid should name the equipment and its expected lead time so the schedule is realistic from the start.

Planning the outage

The cutover from the old service to the new one requires the power to be off. For a business, the timing of that outage matters as much as anything else in the project. With planning, most of the new equipment can be installed and prepared while the old service stays in use, so the actual outage covers only the final connections and the utility's part. That outage can often be scheduled for a night or a weekend.

• Set the outage date with the utility and with the business at the same time.
• List the equipment that must be shut down and restarted in order, such as refrigeration, servers and controls.
• Plan for temporary power if any load cannot be without power for the length of the outage.
• Have the inspection scheduled so the power can be restored as soon as it passes.

If part of the building has to stay on through the cutover, a temporary or permanent standby source may be part of the plan. Our commercial standby generators page covers that work.

Permit and inspection

Inside the city, commercial electrical permits go through the City of San Antonio Development Services Department, and the suburban cities run their own permit offices. San Antonio adopted the 2023 National Electrical Code effective May 1, 2025. A service upgrade is inspected before the utility reconnects, so the inspection is part of the outage plan, not something to arrange afterward. We pull the electrical permit, schedule the inspection and meet the inspector.

A realistic timeline

A service upgrade follows a sequence: the load calculation, the design of the new service, the utility request, equipment ordering, the permit, the installation of everything that can be done while the old service stays live, the planned outage and cutover, the inspection, and the utility's reconnection. The utility's review and work, and the lead time on larger equipment, usually set the overall pace. A clear schedule from the start lets the business plan around the outage instead of being surprised by it.

• Load calculation and scope.
• Utility request and equipment orders.
• Permit.
• Installation while the old service stays in use.
• Planned outage, cutover and inspection.
• Utility reconnection and restart of equipment.

What a clear bid includes

A good bid for a service upgrade names the load calculation and its result, the new service size, the equipment and its lead time, the customer side work, the coordination with the utility, the permit and inspections, and the outage plan. It also says what is excluded, such as utility charges the utility bills directly. At Wattsmith every job gets a written bid, and any change is priced in writing and approved before the work is done.

For panel work at home, see our panel upgrades page. For the rest of what we do for businesses, see our commercial electrical services page, and if the reason for the upgrade is new chargers, our guide to commercial EV charging cost and incentives covers the planning.