Ask ten Central Texas homeowners what they want a home battery to do, and nine will give some version of the same answer: keep the air conditioning running. In August, that is the whole question. A dark refrigerator is an inconvenience. A house at 96 degrees with no way to cool it is something else.
It is a fair question, and it has a real answer — but not a one-word one. Whether a battery will run your AC depends less on the brand on the wall than on two numbers most homeowners never get explained to them. Here is how we walk through it on a site visit.
Backup power comes down to two different numbers
Every battery is described with two specifications, and they answer two completely different questions. Mixing them up is the most common reason a backup system disappoints its owner.
Power (kilowatts) — what it can run at the same time
Power is the size of the pipe. It determines how much can be switched on at once: the AC compressor, the well pump, the oven, the microwave, all drawing simultaneously. If a load demands more power than the battery can deliver at that instant, the system protects itself and drops the load. This is the number that decides whether your air conditioning starts at all.
Energy (kilowatt-hours) — how long it can keep going
Energy is the size of the tank. It determines duration: how many hours of the outage you can cover before the battery is empty. A battery can have plenty of energy and still be unable to start a compressor, or start it easily and run out by 2 a.m. You need both numbers to be right, and they are sized independently.
Why air conditioning is the hard part
A central AC compressor draws far more current in the instant it starts than it does while it runs. That startup surge is brief, but the battery has to cover it — and it is what separates a system that carries your AC from one that trips trying.
Two things change that math in your favor. A variable-speed or inverter-driven AC ramps up gently instead of slamming on, which dramatically reduces the surge. And a soft starter — a relatively small device added at the condenser — can smooth the startup on a conventional single-stage unit. Which of these applies to your home depends on the equipment you already own, and it is one of the first things we check.
This is also why we ask what your AC actually is before we talk about batteries at all. Sizing backup power without knowing the largest load in the house is guesswork.
“Whole-home” and “critical loads” are a choice, not a tier
Whole-home backup means the entire panel stays live and nothing in the house behaves differently during an outage. Critical-load backup means a selected group of circuits — typically the AC or a mini-split, the refrigerator, well pump, internet, lighting, and a few outlets — stays powered while the rest goes dark.
Neither one is the upgrade. They are different answers to a real trade-off: whole-home requires more capacity to cover every load simultaneously, while critical-load stretches the same stored energy much further because less is drawing from it. Plenty of Hill Country homes are better served by a well-chosen critical-load design that runs for a day and a half than by a whole-home configuration that runs everything for a few hours. We would rather tell you that than sell you the bigger number.
If you want to see how the sizing math works before anyone visits, our home battery sizing guide walks through it, and the whole-home backup page covers what full-panel coverage involves.
Three things worth checking before you shop
- Your AC type. Find the model number on the outdoor condenser. Variable-speed and two-stage units are considerably easier to back up than older single-stage equipment.
- Your panel. Backup systems need physical room and correct breaker capacity. An older or fully populated panel may need attention first — better to know now than mid-project.
- What you actually need powered. Walk the house and make the list. Most people find it is shorter than they assumed, and a shorter list means a longer runtime.
If you already have solar
Adding storage to an existing array is often possible, and it changes the arithmetic considerably: during a summer outage, the sun recharges the battery through the day while it discharges through the evening. Whether it works on your system depends on your inverter and how the array is wired — some pair straightforwardly, some need an additional component. We confirm that on site rather than over the phone, because getting it wrong is expensive.
We are certified on Enphase and FranklinWH, Generac-certified on the standby side, and we service Tesla Powerwall systems — and we are equally willing to tell you that a standby generator is the better fit for your home. A comparison of the three battery platforms is on our home battery comparison page.
The straight answer
Yes, a properly sized home battery can run air conditioning through a Central Texas outage. Whether your battery will run your AC depends on the compressor you have, the loads you want covered, and the runtime you expect — which is why we size the system to the house instead of the other way around.
If backup power is on your mind before the next storm season, book your assessment. We will look at your panel, your AC, and your priorities, and give you an honest read on what it takes to keep your home comfortable when the grid is not cooperating.
Aether Energy is a licensed electrical contractor (TECL #35881) serving Austin, Kyle, Buda, San Marcos, New Braunfels, and the surrounding Hill Country. (210) 394-3961.
