Key takeaways
- A home battery backup stores electricity and powers selected circuits during an outage without fuel, while a standby generator runs as long as it has gas.
- Most battery installs back up an essential loads subpanel rather than the whole house, because air conditioning and electric heat drain a battery quickly.
- A home battery backup works without solar by charging from the grid, but solar is what lets it recharge during a multi-day outage.
- The electrician's work covers the interconnection, the critical loads subpanel, the permit and coordination with CPS Energy where solar is involved.
- Wall or roof mounting questions that go beyond a standard install are structural questions, and they belong with a licensed engineer.
You are looking at home battery backup because the last outage was long enough to make you think about the next one. You want the refrigerator, the lights, the internet and some heat or cooling to keep running, without a generator rumbling in the side yard. The stake is simple: a battery that is sized and wired well carries you through, and one that is not dies in the first evening.
This guide covers the decisions that matter before anyone talks brand: battery or generator, whole home or essential loads, with solar or without. Then it explains the electrician's part of the job in San Antonio, which is where a good battery becomes a working backup system.
Home battery backup or a generator for Texas outages
Texans remember the February 2021 winter storm, when outages lasted for days across much of the state. That event reshaped how many San Antonio owners think about backup power, and the first question is usually whether a battery or a standby generator is the better answer.
A standby generator runs on natural gas or propane and keeps producing power as long as fuel reaches it. On a natural gas line that can mean days. It handles large loads such as central air conditioning well when it is sized for them. It makes noise, it needs exercise and maintenance, and it does nothing for you on a normal day.
A home battery backup stores a fixed amount of energy. It switches over quickly and quietly, it needs little maintenance, and with solar it can recharge every day the sun is out. Without solar, it delivers what it stored before the outage and then stops until the grid returns. It can also be used daily to shift when your house draws from the grid, which a generator cannot do.
The plain comparison: a generator wins on duration when there is no sun, and a battery wins on quiet, daily usefulness and pairing with solar. Some owners install both. The right choice depends on how long you need to ride through and what you need running.
If a generator is still on the table, compare the options in our guide to generator options for San Antonio homes, and see how we install them on our generator installation page.
Whole-home backup versus an essential loads panel
This is the decision that most affects whether a battery does its job. A battery has two limits. One is how much energy it holds, which decides how long it runs. The other is how much power it can deliver at once, which decides what it can start and run together.
Central air conditioning, an electric range, an electric water heater, a dryer and electric strip heat are all large loads. A battery asked to run the whole house, air conditioner included, will either refuse to start the largest loads or drain fast enough to be gone by midnight. That is why most battery installs use an essential loads panel.
An essential loads panel, also called a critical loads subpanel, is a separate panel fed through the battery system. We move the circuits you choose into it: the refrigerator, a few lighting circuits, the internet equipment, the furnace blower on a gas furnace, a bedroom or two, the garage door opener, perhaps a well pump. Everything else stays in the main panel and goes dark in an outage. The battery carries only what you chose, and it carries it longer.
Whole-home backup is possible, usually with multiple batteries or with a smart panel that sheds large loads automatically. It costs more and still involves choices during a long outage. For most San Antonio houses, a well-chosen essential loads panel gives the outcome owners actually want.
A smart panel can replace the fixed subpanel with circuit choices you change in an app. We explain how in our post on smart electrical panel cost in San Antonio.
Home battery backup without solar
A home battery backup without solar is a real option, and for some owners it is the right one. The battery charges from the grid, holds that charge, and powers your essential loads when the grid goes down. Installation is simpler because there is no array on the roof and no solar inverter to integrate.
The limit is recharge. Once the battery is drained, it stays drained until power returns. For short and medium outages, the kind caused by a storm cell or a downed line, that is often enough. For a multi-day event, it is not, unless the battery bank is large or you pair it with a small generator.
Many owners start without solar and add it later. If that is your plan, tell us at the start. We will place the equipment and size the conductors so the solar addition does not mean redoing work.
Home battery backup with solar
With solar, the battery recharges whenever the sun is up, which changes what a multi-day outage looks like. A sized system can keep essential loads running through the night and refill during the day. On normal days, the battery can store solar production for use in the evening.
Solar also adds a step with the utility. Any system that can send power back to the grid needs interconnection approval from CPS Energy before it is switched on for permanent operation. That process covers the solar array and the battery system together, and it is separate from the city electrical permit.
Solar and batteries both land in your panel. Read is your panel ready for solar in San Antonio before you sign anything, and call us if the answer is unclear.
What the electrician does on a battery installation
The battery itself is a box on a wall. Turning it into a backup system is electrical work, and it is most of the job.
- Interconnection: connecting the battery system to your electrical service so it can charge, so it can isolate your house from the grid during an outage, and so it never sends power onto a line a utility worker believes is dead.
- The essential loads subpanel: installing the new panel, moving the chosen circuits into it and labeling everything so you know what will run in an outage.
- Conductor and breaker sizing: making sure every connection is rated for the current the battery can deliver and the code requires.
- Grounding and bonding: bringing the system into line with the grounding of the rest of the house.
- Permit and inspection: pulling the electrical permit and meeting the inspector.
- CPS Energy coordination: handling the utility side where solar is involved, and any service disconnect the work requires.
The essential loads panel is priced from our book like any subpanel, starting at the Subpanel installation, 60A task, from $1,859 for a typical install near the main panel, with circuit moves and the battery interconnection listed on the same written quote. Starting price. Your tech confirms the final number on site before any work.
We do not sell battery brands in this post, and we do not quote battery prices here, because the hardware price is set by the manufacturer and changes. What we quote flat is our electrical work, and we quote it before work starts.
What makes up home battery backup cost
Home battery backup cost comes in layers, and seeing them separately makes quotes easier to compare. The battery hardware is the largest layer, and it scales with how much energy you want stored. A second battery adds runtime and adds cost almost in proportion. The inverter or gateway that manages the switchover may be built into the battery or sold as its own unit, depending on the brand.
The electrical work is the next layer: the essential loads subpanel, moving circuits, the interconnection, conductors and the permit. That layer depends on your house more than on the battery. A panel with room, in a garage next to where the battery will hang, keeps it modest. A full panel, a long distance between the panel and the mounting wall, or a service that needs work first all add to it.
When you compare quotes, ask each installer to separate the hardware from the electrical work and to list which circuits will be backed up. Two quotes for the same battery can differ widely because one backs up four circuits and the other backs up twelve. The circuit list is what you are actually buying.
Sizing comes first: load calculation and capacity
Two calculations decide whether a battery project works. The first is the essential loads list: what you want running, what each item draws, and for how long. That sets the battery size. The second is the service capacity check: whether your existing panel and service can accept the battery interconnection and the subpanel, especially if an EV charger or solar is also going in.
We run both as part of a written load calculation, which our price book lists as the Load calculation and capacity report task, from $709. You get a report signed by a Texas licensed master electrician that you can hand to any battery supplier. Starting price. Your tech confirms the final number on site before any work.
Our published prices are all on the pricing page. If you want to spread the cost, see financing.
Mounting: walls, garages and structural questions
Home batteries are heavy, and where they go matters. Most are mounted on a garage wall or an exterior wall near the main panel, on a pad or a bracket the manufacturer specifies. The manufacturer also sets clearances, and the inspector checks the install against those instructions and the code.
When a mounting question goes beyond a standard install, such as a wall you are not sure can carry the weight, an older structure, or a roof that will take a new solar array, it is a structural question. Wattsmith is not an engineering firm. Our sister firm, 254 Engineering (Texas Board of Professional Engineers and Land Surveyors firm F-29811), handles foundation and structural evaluations.
For a structural evaluation, contact 254 Engineering. For the electrical work, we coordinate with them so the two sides fit together.
How we handle a home battery backup installation
Wattsmith Electric is veteran-owned and licensed by TDLR under TECL 41806. On a home battery backup project we start with the essential loads list and the load calculation, give you a flat written price for the electrical work before anything starts, pull the permit, meet the inspector and handle CPS Energy coordination where solar is part of the system. You choose the circuits. We make sure they are the ones that run when the grid goes down.
Call us and we will tell you over the phone whether a visit is the next step. To schedule, contact Wattsmith Electric. If you are in the Hill Country, our generator readiness guide for Timberwood Park and Bulverde covers the backup questions specific to those areas.