Why Your East Texas AC Runs Constantly (And What To Do About It)

You probably noticed it sometime in late May. Your AC started running at 7 in the morning and didn't shut off until after midnight. The house stayed *almost* comfortable—maybe 76 degrees when you really wanted 72—but your electric bill hit $380 for a 1,800-square-foot home. If you're in Dayton, Crosby, or Mont Belvieu, you've heard the same story from three neighbors on your street. One guy swears his system hasn't cycled off in four days straight.

Here's what most HVAC contractors won't tell you upfront: a system that runs constantly isn't always broken, but it's almost always costing you serious money. Sometimes it's a $150 fix. Sometimes it's a $7,000 mistake that happened when your house was built. And sometimes—this is the part that makes me angry—it's a deliberate undersizing decision a contractor made in 2018 to save himself $400 on equipment while sticking you with the consequences every summer for the next fifteen years.

I've been doing HVAC work in East Texas since before Hurricane Rita, and I've seen the same five problems cause 90% of the constantly-running systems in Liberty and Chambers counties. Let's go through each one, what it actually costs to fix, and what I'd do if it were my house and my money.

Is Your AC Actually Undersized for Your Home?

Your AC is probably undersized if it was installed between 2015 and 2020 in a new construction neighborhood, and yes, this was often intentional. Builders in fast-growth areas like Mont Belvieu routinely spec'd 2.5-ton units for 1,600-square-foot homes that actually needed 3 tons, because saving $600 per house across 200 homes adds up to real money in their pocket. You're the one paying for it now.

A properly sized AC in East Texas should cycle off for 8-12 minutes every hour on a 95-degree afternoon. If yours runs continuously from 2 PM to 9 PM and never hits your setpoint, you're undersized by at least half a ton. The Manual J calculation that's supposed to determine proper sizing accounts for insulation, window area, ceiling height, and orientation—but I've reviewed probably forty load calculations from Liberty County tract homes in the past three years, and maybe six were actually correct.

Here's the real test: if your system was installed after 2010 and runs nonstop on 97-degree days but keeps your house within 3 degrees of setpoint, it's borderline but functional. If it runs nonstop and you're still 5+ degrees above setpoint, you're genuinely undersized and need to replace the outdoor unit and possibly the air handler. That's $4,200 to $6,800 depending on whether your ductwork can handle the increased airflow. I know that's not what you want to hear, but running an inadequate system for another five summers will cost you $1,200+ annually in excess electricity costs compared to a right-sized unit.

The calculation matters here: a 2.5-ton unit draws about 3,500 watts. Running continuously for 12 hours daily throughout June, July, and August means 3,780 kWh of usage. At $0.13/kWh (typical Entergy Texas rate), that's $491 just for AC in those three months. A properly sized 3-ton unit that cycles normally might run 8 hours daily at 4,000 watts—2,160 kWh, or $281. You're spending an extra $210 every summer, and that doesn't account for the refrigerant leaks and compressor wear that come from never shutting down.

How Much Are Duct Leaks Actually Costing You?

Duct leaks waste 23-38% of your conditioned air in most East Texas homes built before 2000, and I can prove it in about twenty minutes with a $40 smoke pencil. Those leaks are in your attic, where it's currently 138 degrees at 3 PM in July, which means you're paying to cool the underside of your roof sheathing instead of your living room.

The worst leaks are at the boot connections where floor registers connect to the main trunk line, and at the plenum takeoffs right near the air handler. I've found gaps you could fit three fingers through on homes in Highlands and Dayton. The builder's crew connected flex duct with one wrap of foil tape, it failed after eighteen months, and now 140 CFM of cold air is dumping into your attic every time the blower runs. Your system can't keep up because 30% of its capacity is being piped directly into the space you don't live in.

Duct sealing costs $800 to $1,400 for a whole-house job if you hire it out. The contractor will use mastic (the thick paste that actually works) on all the metal connections and mechanical fasteners plus mastic on the flex duct connections. Foil tape alone isn't enough—it fails in high heat and humidity within two to four years. I've seen this repair pay for itself in 14 months on a 2,200-square-foot home in Baytown where the homeowner's summer bills dropped from $410/month to $290/month.

You can DIY about 60% of this work if your attic is accessible and you're willing to spend four miserable hours up there in early morning before it becomes an oven. Get actual mastic from a supply house, not hardware store "duct sealant." Check every single connection point you can reach. The return plenum is especially critical—any leak there is pulling hot attic air into your system, which means your AC is fighting to cool 95-degree air instead of 78-degree air from your hallway.

What's the Real Story With Your Attic Insulation?

Your attic has R-19 fiberglass batts when it needs R-38 blown cellulose, and this matters more in East Texas than almost anywhere else because our cooling season runs from April through October. That's seven months of your attic reaching 125-145 degrees while your AC tries to keep the ceiling below that temperature. Inadequate insulation means heat radiates right through into your living space faster than your system can remove it.

Most homes built in the 1980s and 1990s in Liberty and Chambers counties have 6 inches of fiberglass between the joists. That's R-19 on a good day, R-15 after it's been compressed and disturbed and gotten damp a few times. Texas code now requires R-38 in our climate zone, which means 12-14 inches of blown insulation. Upgrading from R-19 to R-38 typically reduces ceiling heat gain by 48-52%, which directly translates to fewer hours of runtime.

Adding 8 inches of blown cellulose over existing fiberglass costs $1.10 to $1.65 per square foot depending on attic accessibility. For a typical 1,600-square-foot home, that's $1,760 to $2,640 for material and installation. The payback period in East Texas is 3.5 to 5 years based purely on cooling cost reduction—faster if you're in an older home with minimal existing insulation.

Here's what I actually did on my own house in 2019: hired a crew to add 10 inches of cellulose to bring total coverage to R-42. My June electric bill dropped from $334 to $251 the following year with identical thermostat settings and similar weather. The work cost $1,980 for 1,740 square feet of attic. I've saved roughly $900 over four summers, so I'm almost paid back.

The radiant barrier question comes up constantly. Those foil sheets stapled to the underside of your roof rafters reduce radiant heat transfer by 30-40% but do nothing for conductive heat transfer through inadequate insulation. If you're choosing between radiant barrier ($650-900 installed) and adding 8 inches of insulation ($2,200), add the insulation. If you've already got R-38 and want incremental improvement, then consider radiant barrier. Don't let a contractor talk you into radiant barrier as a substitute for proper insulation—it's not.

How Do You Know If You're Low on Refrigerant?

Your system is probably low on refrigerant if it runs constantly, produces weak airflow at the registers, and develops ice on the copper line running into your house. The refrigerant didn't "run out"—it leaked, and it's still leaking right now, and just adding more refrigerant without fixing the leak is throwing away $275 every eighteen months.

Low refrigerant reduces cooling capacity by roughly 15% for every 10% undercharge. If you're 20% low, your 3-ton system is effectively performing like a 2.5-ton system, which means it runs longer to achieve the same cooling. The compressor also runs hotter and works harder, which takes years off its lifespan. I've seen compressors fail at 9 years that should have lasted 16, and the autopsy always shows the same thing: chronically low refrigerant charge and the high head pressures that come with it.

The leak is usually at a brazed joint or a schrader valve. In East Texas, I see a lot of leaks where the lineset enters the outdoor unit, because the brazing work was rushed during initial installation and there's a pinhole that takes 3-5 years to become symptomatic. Finding and fixing a leak costs $450 to $850 depending on location and whether the coil itself is leaking (much more expensive). Then you need to recharge the system—figure $275 to $380 for the refrigerant and labor to properly evacuate and charge by weight, not by pressure.

Some contractors will offer to "top off" your charge for $185 without doing leak detection. This is short-term thinking that costs you more money. The leak continues, the refrigerant escapes again, and you're paying for another top-off next year. Fix the leak first, then charge the system properly. If the leak is in the evaporator coil and repair would cost $1,400, and your system is 13+ years old, that's when you need to have a serious conversation about replacement instead of repair.

One specific warning for coastal Chambers County homes near Anahuac and Baytown: salt air accelerates coil corrosion. If your outdoor unit is within a half-mile of the bay or Trinity River delta, expect shorter coil life—sometimes 10-12 years instead of 15-18. Budget accordingly.

Is Your Thermostat Lying to You About Your Home's Temperature?

Your thermostat is mounted on the hallway wall directly across from the return air grille, which means it's reading the coldest air in your house and shutting down your system while your bedrooms are still 79 degrees. This is a $90 problem with a $0 diagnosis, and it's shockingly common in tract homes throughout Liberty County.

The thermostat needs to read average home temperature, not the temperature of the specific 6-square-foot area where some HVAC installer found an existing wire. Mounting it near the return grille means it's sampling air that just came from the coldest register in your house. The thermostat thinks you're at 73 degrees, clicks off, and meanwhile your master bedroom at the end of the duct run is still sitting at 77 degrees. Your AC never runs long enough to satisfy the whole house.

Relocating a thermostat costs $85 to $140 depending on how far you're moving it and whether there's already a wire path. You want it on an interior wall, away from windows, away from registers, away from the return grille, and away from heat sources like the kitchen or west-facing exterior walls. Five feet down the hall can make a 3-degree difference in how your system maintains temperature.

The other thermostat problem I see constantly: ancient programmable thermostats from 2008 with failing temperature sensors. The sensor reads 2-3 degrees cooler than actual temperature, so your house stays warmer than you set it. Replacing with a basic non-smart thermostat costs $45 for the hardware and 20 minutes of your time. You don't need a $230 WiFi learning thermostat—you need accurate temperature sensing and reliable switching. I'm still running a $62 Honeywell programmable in my house and it's been flawless for six years.

What About Dirty Filters and Coils?

Your filter is probably clogged right now, and yes, this absolutely causes extended runtimes. A restricted filter reduces airflow across the evaporator coil, which reduces heat transfer, which reduces cooling capacity, which means your system runs longer to cool the same space. It also causes the evaporator to ice up, which further restricts airflow in a vicious cycle.

Replace your filter every 30-45 days during cooling season in East Texas. I don't care what the package says about "90-day filters"—our pollen counts, humidity, and longer cooling season means filters load up faster here than in drier climates. A $4 filter replaced monthly performs better than a $22 filter replaced quarterly. Use MERV 8 pleated filters for standard systems; don't jump to MERV 13 unless your system was specifically designed for the increased static pressure.

The evaporator coil inside your air handler needs cleaning every 3-4 years in our climate. That coil gets a film of dust, pollen, and organic matter that acts as insulation, reducing heat transfer efficiency by 20-30% when it's heavily loaded. Professional coil cleaning costs $180-240 and takes about 90 minutes. They'll remove the access panel, spray the coil with a foaming coil cleaner, rinse it, and verify proper drainage.

You can inspect your own evaporator coil if you're comfortable removing the access panel on your air handler. Shine a flashlight through the fins—if you can't see light clearly passing through, the coil is dirty enough to affect performance. Don't use a pressure washer or harsh chemicals; you'll damage the fins. If you're DIYing it, use actual coil cleaner from a supply house and follow the directions about dilution and contact time.

The outdoor condenser coil is easier to access but equally important. Cottonwood seed, grass clippings, and oak pollen cake onto those fins every spring in East Texas. Rinse it gently from the inside out with a garden hose every April and September. If you use a pressure washer, keep it at low pressure and spray straight on, never at an angle that could bend the fins.

What Actually Works: Your Priority List

Start with the cheap fixes that have immediate payback. Replace your filter today if it's been more than 45 days. Check your outdoor unit for debris and rinse the condenser coil if it's visibly dirty. These two things cost under $20 and might reduce your runtime by 12-18%.

Next, get your thermostat location evaluated. Spend 15 minutes with a $12 digital thermometer checking temperatures in different rooms while your system is running. If there's more than a 4-degree spread between rooms, you've either got duct problems or a thermostat placement problem. Moving the thermostat is cheaper, so check that first.

If you're still running constantly after filters and thermostat location are ruled out, call for a service visit specifically to check refrigerant charge and look for duct leaks. This diagnostic call costs $89-125 at most honest companies. Make sure they check superheat and subcooling, not just static pressure—actual refrigerant charge verification requires temperature measurements. If they find a leak, get the repair quote in writing with the specific location of the leak identified.

For older homes with minimal attic insulation, adding blown cellulose is your next move. This has a 4-year payback and makes your house more comfortable immediately. Do this before you consider replacing equipment, because proper insulation reduces the required system size, which saves you money on the replacement.

System replacement comes last. If your unit is 14+ years old, undersized, and would need refrigerant leak repair plus duct sealing to work properly, the math usually favors replacement with a correctly sized system. You're looking at $5,800 to $7,400 for a proper 3-ton replacement with a reputable contractor in East Texas. Don't let anyone talk you into a 5-ton unit for a 1,600-square-foot home—oversizing causes short cycling, poor dehumidification, and premature failure.

Get three quotes. Ask each contractor to show you their Manual J calculation. If they estimate tonnage by square footage alone ("you need one ton per 500 square feet"), cross them off your list immediately. Ask what brand of equipment they install most and why—if the answer is "whatever's cheapest that week," keep looking. You want someone who installs mostly one or two brands and can explain their reasoning.

And one final thing: if a contractor tells you your constantly-running AC just needs a "tune-up" for $350, get a second opinion. Tune-ups don't fix undersized systems, major duct leaks, or refrigerant leaks. They're maintenance, not repair. Don't let someone sell you an oil change when you need new tires.