Shrink the Battery You Need: 8 Load Cuts to Make Before Sizing

The cheapest kilowatt-hour you will ever buy is the one you never have to store. Before anyone picks a battery size, it pays to ask a boring question first: how much power does this house actually want during an outage? In Houston the honest answer is "a lot, mostly for cooling."

That means the house itself is the first lever. A tighter attic, a cleaner air filter and a smarter thermostat all shrink the load your backup system has to carry. Below are eight cuts to make before you size anything, each tied to a published U.S. government source.

Key Takeaways

• Cooling is the biggest swing load in a Texas home, so most of the cuts below target the AC.
• Government sources put savings from single measures between roughly 5% and 90%, depending on the measure and the house.
• Efficiency shrinks the battery you need. It does not replace storage.
• Size the system after the cuts, using your real loads.

Why does cutting load come before battery sizing?

Battery size follows load. If a house draws 5 kW with the AC running and 1.5 kW without it, the battery you need for the same number of hours changes by a factor of more than three. Every cut you make upstream compounds into a smaller, simpler system.

Texas households are heavy users to begin with. The U.S. Energy Information Administration's state energy brief for Texas reports that air conditioning takes a larger share of household energy in Texas than the national average, and that more than 80% of Texas homes use central air. That survey is from 2009, so treat the exact percentages as a rough guide, not a current measurement. The direction is still right: in Houston, the AC is the load.

Our Texas battery sizing guide owns the sizing method itself. This article is the step that comes before it. If you want to see how AC tonnage translates into watts, the central AC tonnage sizing post covers that.

Cut 1: Does a thermostat setback really lower the load?

The U.S. Department of Energy says you can save as much as 10% a year on heating and cooling by turning your thermostat back 7 to 10 degrees Fahrenheit for 8 hours a day from its normal setting. That figure is an annual average for a house that is empty or asleep during the setback.

For backup planning, the useful part is behavioral. During an outage you control the setpoint. Holding the house at 80 instead of 74 changes how hard the compressor works, and a smart thermostat makes that a one-tap habit. Note that DOE's number is annual, not per-outage. Do not promise yourself 10% in a storm.

Cut 2: How much does a clean air filter help?

The DOE reports that replacing a dirty, clogged air filter with a clean one can lower an air conditioner's energy consumption by 5% to 15%. It is the cheapest item on this list and takes five minutes.

Houston's long cooling season means filters load up faster than most homeowners expect. Put a calendar reminder on it. A coil cleaning and a refrigerant check by a licensed HVAC technician belong in the same visit, though DOE's quoted range applies specifically to the filter.

Cut 3: Are your ducts leaking your cooling away?

ENERGY STAR states that in a typical house, about 20 to 30 percent of the air moving through the duct system is lost to leaks, holes and poorly connected ducts. In Houston, many ducts run through a hot attic, so a leak is a direct hit on the AC's workload.

Sealing ducts is a contractor job when the leaks are inside the attic or walls. It is also one of the few cuts that helps both comfort and runtime. We have not found a public Houston-specific savings figure for duct sealing, so we are not quoting one.

Cut 4: What does sealing and insulating the attic do?

The EPA estimates that homeowners can save an average of 15% on heating and cooling costs, or about 11% on total energy costs, by air sealing and adding insulation in attics, floors over crawl spaces and accessible rim joists. ENERGY STAR notes that savings vary by climate and are modeled on typical existing homes.

Those numbers are national averages, and ENERGY STAR says estimated savings are higher in the North than the South. For a Houston home, read 15% as an upper reference, not a promise. The attic is still the right place to start, because that is where summer heat enters the house.

Cut 5: Is a radiant barrier worth it in Houston?

The DOE says some studies show radiant barriers can reduce cooling costs 5% to 10% in a warm, sunny climate, and that they work best in hot climates, especially when cooling ducts run through the attic. The same page notes the reduced heat gain may even allow a smaller air conditioner.

That last point matters for backup sizing. A smaller AC means a smaller starting surge. Our AC tonnage post explains why surge, not only running watts, drives inverter sizing. Keep in mind DOE hedges its wording with "some studies," so treat 5% to 10% as a range, not a guarantee.

Cut 6: Should you replace an electric water heater?

The DOE's building science resources say heat pump water heaters can be two to three times more efficient than conventional electric-resistance water heaters. A standard electric tank is one of the largest single loads in a home, so a heat pump unit can shrink both daily kilowatt-hours and the connected load.

If you are deciding whether to back up a water heater at all, read our electric water heater backup guide. For many households, the cheapest answer is to leave a resistance heater off the backed-up circuits, or replace it with a heat pump model and then protect it.

Cut 7: Do LEDs still matter?

The DOE reports that residential LEDs, especially ENERGY STAR rated products, use at least 75% less energy and last up to 25 times longer than incandescent lighting. Most Houston homes have already converted, but closets, garages and outdoor fixtures are common holdouts.

Lighting is a small slice of an outage load, so do not expect a dramatic change in battery size from this one. It is still worth doing because it is nearly free and permanent. Think of it as cleanup, not a headline lever.

Cut 8: What about the pool pump?

A Houston pool pump can be one of the biggest scheduled loads outside the AC. According to the DOE's Pacific Northwest National Laboratory, a variable-speed pool pump can reduce pool pump energy use by 50% to 90%. The same guide describes a typical 1.5 horsepower single-speed pump drawing about 2,000 watts while running.

The physics are why. Cutting pump speed by 30% drops power by roughly 70%, per that guide's affinity-law example. In an outage you can simply stop the pump, but if you want filtration to keep running on stored power, a variable-speed unit makes that realistic.

How much smaller will the battery get?

Here is the honest part. No public source gives a single, reliable "your battery shrinks by X%" figure for a Houston home, and we will not invent one. Each cut above has its own published range, they overlap, and they depend on your house.

What we can show is the arithmetic. Eos modules are 9 kWh nominal with 8.76 kWh usable, per our plan data, and the controller delivers 11.5 kW continuous with 17.1 kW surge. Suppose your cuts remove 1 kW of average load over a 12 hour outage. That is 12 kWh you no longer need, which is more than one full module. That is an illustration of the math, not a prediction for your home.

What efficiency cannot do

Efficiency shrinks the system. It does not replace it. A perfectly tuned house still loses power when the grid goes down, and a refrigerator, Wi-Fi and a medical device still need stored energy.

The second limit is that some loads are not negotiable. Air conditioning in a Houston August is a safety question for many households, not a luxury. Prioritizing circuits through a smart panel is the other half of the strategy, and our circuit prioritization guide shows how to decide what runs and what waits. You can also look up common figures in the appliance wattage chart.

One more note on regulation, since people ask. Texas SB 1252, effective September 1, 2025, bars cities from adopting or enforcing rules that regulate the installation or inspection of a residential energy backup system, defined as one providing no more than 50 kW or storing no more than 100 kWh (TDLR). Work still must be done by licensed Texas electrical contractors. Your utility's interconnection rules are a separate matter.

A simple order of operations

1. Replace the AC filter and set the outage setpoint you will actually hold.
2. Have ducts and attic checked, then seal and insulate where needed.
3. Add a radiant barrier if the attic is bare and the ducts run through it.
4. Swap resistance water heating or schedule it out of the backed-up circuits.
5. Convert remaining bulbs and slow the pool pump.
6. Then size the battery, using your remaining loads.

You do not have to finish every cut first. Some, like attic work, take weeks. Start the planner now, and revisit sizing after the work is done.

Or call Eos at 833-989-3737 to talk through your setup with an installer.

Frequently Asked Questions

Should I do efficiency upgrades before buying a battery?

Usually yes for the cheap ones. A filter, a thermostat habit and sealed ducts cost little and lower your load right away. Larger jobs like attic insulation can run in parallel with battery planning, since you can size with today's loads and adjust.

Can efficiency upgrades replace a home battery?

No. Upgrades reduce how much energy you use, but they do nothing when the grid is down. A battery is the only item on this list that supplies power during an outage. Efficiency makes the battery smaller and the runtime longer.

Which cut matters most in Houston?

Anything that reduces the cooling load, because the AC dominates summer demand. The DOE reports a 5% to 15% drop in AC consumption from a clean filter, and 5% to 10% from a radiant barrier in sunny climates. Your attic and ducts decide the rest.

Does a smart thermostat help during an outage?

It helps if you use it to hold a higher setpoint. DOE's 10% a year figure applies to a regular 7 to 10 degree setback for 8 hours a day, so do not read it as an outage guarantee.

Will the planner account for these cuts?

The planner asks about your home and your priorities, then recommends a size. You can tell the planner what you have already done, or plan to do, and revisit the size after upgrades.