If you want one number, set your air conditioning to 78°F when you are home and awake, and raise it 4 to 7 degrees when the house is empty. That single change, held consistently through a North Texas summer, does more for your electric bill than almost anything else you can do without spending money on equipment. The rest of this comes down to how you manage the setback, not chasing a lower number.
What Is the Best Thermostat Setting for a Texas Summer?
78°F is the number the U.S. Department of Energy points to as the sweet spot between comfort and energy use, and it holds up in Denton County summers too, even with triple-digit afternoons. Every degree you lower that setpoint adds roughly 3 to 5 percent to your cooling costs, and that adds up fast across a four-month stretch of real Texas heat. If 78°F feels too warm at first, most households adjust within a week or two, especially if you pair it with ceiling fans, which let you feel comfortable at a higher setpoint because moving air feels several degrees cooler than still air.
The mistake we see constantly is setting the thermostat to 70°F or lower hoping the house will cool faster. It will not. Your system runs at the same capacity regardless of how low you set it, so a lower number only means it keeps running longer after the house is already comfortable, with no benefit except a higher bill.
Should You Use a Setback Schedule, and What Should It Look Like?
Yes, and this is where most of the real savings come from. Here is a simple schedule that works for most two-income households in the metroplex:
| Time | Setting | Why |
|---|---|---|
| Home, awake (6am-8am, 5pm-10pm) | 77-78°F | Comfortable range, system not straining |
| Away at work (8am-5pm) | 82-84°F | Setback saves energy without fully heat-soaking the house |
| Overnight (10pm-6am) | 76-77°F | Slightly cooler for sleep, still efficient |
The key is a setback of 4 to 7 degrees while you are out, not a full shutoff. Turning the AC off entirely during a 95°F day lets heat soak deep into drywall, furniture and your attic insulation, especially with the attic furnaces and ductwork common in North Texas homes sitting in 140°F attic air all day. By the time you get home, your system has to fight that stored heat on top of cooling the air, which takes longer and uses more energy than a moderate setback would have.
How Do You Program a Setback Without Making the House Miserable When You Get Home?
The trick most people miss is a pre-cooling ramp instead of a single jump. If you program your thermostat to start dropping back toward 78°F about 30 to 45 minutes before you typically arrive home, the house meets you at a comfortable temperature instead of you walking into an 84°F room and waiting it out. Most programmable and smart thermostats support multiple schedule points per day for exactly this reason. A smart thermostat with geofencing does this automatically based on your phone's location instead of a fixed clock, which matters if your schedule varies day to day.
Does Humidity Change What Setting You Should Use?
In the DFW metroplex, yes, more than in a dry climate. Humidity from Lewisville Lake and Lake Ray Hubbard means the air can feel several degrees warmer than the thermostat reads, because your body cools itself through evaporation and that process slows down in humid air. This is why a 78°F reading in a dry house in West Texas feels different from 78°F in a humid house near Lewisville or Highland Village. A dehumidifier or a system with good latent cooling capacity lets you hold a comfortable feel at a slightly higher number, since the air itself feels less damp.
What Setting Actually Lowers Your Electric Bill the Most?
The setback while you are away matters more than the daytime number, because it is the longest stretch of the day. A household that holds 78°F all day but skips any setback saves less than one that runs 76°F while home and 83°F for eight hours at work. ERCOT grid stress during peak summer afternoons also means electricity demand, and sometimes pricing under time-of-use plans, is highest exactly when your system would otherwise be working hardest to fight both the outdoor heat and an empty, heat-soaked house. A setback during those peak hours is doing double duty: lower runtime and avoiding the worst pricing window.
If you want a deeper look at how long your AC should run on a brutally hot day before you should worry something is wrong, we cover realistic runtime expectations there, since a thermostat setting only matters if the system behind it is actually working correctly.
A thermostat setting also cannot fix a system that is already working harder than it should. A dirty filter, a coil losing efficiency from dust, or refrigerant running low all force your system to run longer at any setpoint, which quietly erases whatever you saved by dialing in a smart schedule. That is part of why a seasonal check before summer matters as much as the number on the wall. We walk through a full pre-summer checklist in our spring AC checklist for North Texas homeowners, which covers the mechanical side of the same goal this post covers on the settings side.
Does the Thermostat Setting Matter More Upstairs in a Two-Story Home?
If you live in a two-story house with a single thermostat downstairs, this is where setpoint advice gets complicated, because heat rises and upstairs bedrooms often run 5 to 10 degrees warmer than what the thermostat reads on the main floor. Setting the whole house colder to compensate just means the downstairs gets overcooled while upstairs still struggles. A zoned system, or at minimum balancing your supply registers so upstairs gets more airflow in summer, solves this far better than any thermostat number can. This shows up constantly in newer subdivisions around Frisco, Little Elm and Aubrey with large upstairs square footage and a single return.
Is a Smart Thermostat Worth It Just for the Scheduling?
For most homes, yes, mainly because people stick to a schedule they do not have to think about. A basic programmable thermostat can technically do the same 4-point schedule described above, but most people set it once and then override it constantly, which erases the savings. A smart thermostat's real value is geofencing, usage history that shows you exactly how many hours your system ran last month, and remote adjustment from your phone if your schedule changes unexpectedly. ENERGY STAR's guidance on smart thermostats is a good independent source if you are comparing specific models before buying one.
What Should You Do Next?
Start with 78°F while home, a 4 to 7 degree setback while away, and a 30 to 45 minute pre-cooling ramp before you get back, then give it two weeks before deciding it does not work for your house. If you have followed a setback schedule like this and the house still will not hold a comfortable temperature, that is a sign of a mechanical problem, not a thermostat problem, whether that is a dirty filter, low refrigerant, leaky ductwork, or a system that was undersized for your square footage from the start. R2 Mechanical is a licensed Texas HVAC contractor (TACLB20924E) based in Krum with a 5.0 rating from 86 Google reviews, and we offer a $29 refrigerant check and a $89 AC tune-up if you want a technician to rule out an equipment issue before you blame the settings. Call us at 940-208-5398 or request service online and we will take a look.