What Temperature Should I Have My AC Set At in Edwardsville, IL?

You are staring at the thermostat, the house feels sticky at 72 degrees, your July bill from Ameren just hit $220, and half the internet is telling you to set the AC to 78 degrees while the other half calls that unlivable. If you feel like you have been guessing at the right number for years, that is because the answer is not one number. 

The right setpoint for an Edwardsville home depends on humidity, occupancy, ceiling fans, house age, and what the outdoor dew point is doing that day, none of which the “just set it to 78” advice bothers to mention. 

In this guide, you will get the actual temperature settings the Department of Energy recommends for each part of the day, the humidity number that matters more than the temperature number, what each degree actually costs on your Ameren bill in Edwardsville, and the local factors that push the ideal setting a few degrees in either direction.

Key Takeaways

• The Department of Energy recommends 78 degrees when home, 82 sleeping, and 85 away.
• Every degree lower than 78 raises your cooling bill by roughly 3 to 5 percent monthly.
• Indoor humidity between 40 and 60 percent matters more for comfort than the temperature.
• Bedroom sleep temperature research favors 60 to 67 degrees for the deepest quality rest.
• Ceiling fans let you set the thermostat 4 degrees higher without losing perceived comfort.

The Short Answer: What the DOE Actually Recommends

The Department of Energy’s cooling guidance is straightforward. Set your thermostat to 78 degrees Fahrenheit when you are home and awake, 82 degrees when you are asleep, and 85 degrees when you are away for the day. The DOE energy saver guidance frames these numbers as the baseline for balancing comfort against the cost of running the AC in summer.

The 78-degree recommendation drew enough backlash that the DOE briefly removed the page from its site a few years back before restoring it, and ENERGY STAR has publicly clarified that the agency does not endorse any specific setpoint. That awkward history is useful context. The 78 number is a guideline, not a mandate, and the real answer for your house depends on variables the guideline cannot see.

For most Edwardsville homes with average insulation, the honest usable range for the daytime setpoint is 72 to 78 degrees, with the low end suited to humid stretches when the dew point makes 78 feel worse than the number reads, and the high end suited to dry stretches or homes with strong ceiling fan coverage.

Why 78 Degrees Feels Warmer in Edwardsville Than in Denver

Two identical thermostats set to 78 will produce two very different comfort experiences in Edwardsville versus a dry-climate city, because relative humidity changes how the body sheds heat. 

Summer dew points in Edwardsville regularly climb into the low to mid 70s during July and August, which is a heavy moisture load coming off the surrounding Mississippi and Kaskaskia river basins. High dew points block evaporation off your skin, and a 78-degree room with a 65-degree dew point feels sticky in a way that a 78-degree room in a drier climate does not.

This is the single most misunderstood piece of the ideal-temperature question in Edwardsville. If the house feels miserable at 78 in mid-July, the problem is almost never that the thermostat needs to drop to 70. The problem is that the humidity is too high, and the fix is to run the AC in a way that removes more moisture, not to keep chasing a lower temperature that will not solve the underlying discomfort.

What Each Degree Actually Costs on an Ameren Bill

Every degree you lower the thermostat below 78 raises your cooling costs by roughly 3 to 5 percent, according to widely cited utility and DOE estimates. That number translates directly to Ameren bill math.

If your average summer cooling portion of the electric bill is $140 per month at 78 degrees, dropping to 72 degrees raises the cooling cost by roughly 18 to 30 percent, or $25 to $42 per month. Over the four hardest summer months in Edwardsville (June through September), that is $100 to $170 in extra spending to hold the house six degrees cooler than the DOE baseline.

Reverse the math and it works the same way. Bumping the thermostat from 72 to 75 during work hours cuts roughly 9 to 15 percent off the cooling cost for those hours. Small numbers move real money when they compound across an Edwardsville summer that regularly runs 90-plus degrees for 20 to 30 days.

The takeaway is not that you should suffer at 78. The takeaway is that you should know what any specific setpoint decision actually costs before you make it, so you can pick the tradeoff instead of guessing.

The Best Bedroom Temperature for Sleep

The sleep research pushes hard against the DOE’s 82-degree sleeping guidance. According to the Sleep Foundation, the ideal bedroom temperature for quality sleep is between 65 and 68 degrees Fahrenheit for most adults, with individual variation stretching the range from 60 to 67 degrees at the lower end.

The physiology behind this is simple. Your core body temperature drops by 1 to 2 degrees as you fall asleep, and a cool bedroom accelerates and stabilizes that drop. Rooms above 72 degrees interfere with sleep onset and REM cycle depth, which is why a warm summer night in a poorly cooled house leaves you groggy even after eight hours in bed.

The practical resolution for Edwardsville homeowners is a compromise. Running the whole house at 65 degrees overnight to hit ideal bedroom temperature is expensive and unnecessary. Instead, target 72 to 74 degrees in the main body of the house overnight, and use a bedroom ceiling fan, a bedroom fan, or a targeted mini split to pull the sleeping space down another 4 to 6 degrees. Households with the option to zone the upstairs separately from the downstairs get the best of both approaches.

Humidity: The Number That Matters More Than Temperature

If you fix nothing else about your AC setup this summer, fix the humidity. The EPA and ASHRAE both recommend indoor relative humidity between 40 and 60 percent, and specifically the 40 to 50 percent range in summer for optimal comfort and mold prevention.

Below 30 percent, indoor air dries out skin, sinuses, and eyes. Above 60 percent, mold spores can germinate on drywall and dust mites multiply in bedding and carpet. The mid-range is not a preference. It is a health target that the EPA has published guidance on for years as part of its indoor air quality work.

Central AC removes humidity as a byproduct of cooling, but the effectiveness varies wildly with system sizing, run time, and airflow. If your Edwardsville home consistently runs above 60 percent humidity even with the AC running, the likely causes are an oversized AC that short-cycles before removing moisture, a dirty coil that cannot transfer heat efficiently, or a lack of return airflow. 

A whole-house dehumidifier is the reliable fix in stubborn cases, and it lets you raise the thermostat setpoint 2 to 4 degrees while feeling more comfortable, which recovers much of its own cost through lower cooling bills.

Buy a $15 hygrometer for the main living space and check the humidity number every few days during summer. That reading will tell you more about whether your AC is working properly than the temperature number ever will.

Setpoints by Occupancy State: A Practical Guide

The right AC setting is not a single number for the whole day. It is four or five numbers matched to how the house is being used at that hour.

Home and awake: 74 to 78 degrees. Use the lower end when humidity is above 55 percent or the day is above 90 degrees outside. Use the higher end when ceiling fans are running and the house is well shaded.

Home and asleep: 70 to 74 degrees in the main house, with a bedroom fan or upstairs zoning pulling the sleeping space to 65 to 68 degrees. Households running a whole-house setpoint of 68 to 70 overnight will get better sleep at a real energy cost that they should size against the sleep benefit.

Away for the workday (six to nine hours): 80 to 82 degrees. This is the sweet spot for real savings without a massive recovery cost when the AC has to pull the house back down at the end of the day.

Away for a weekend or vacation: 82 to 85 degrees. Do not turn the AC off entirely in an Edwardsville summer. A house left at 90 degrees for three days can develop indoor humidity above 70 percent, damage wood floors and cabinetry, and take a full day of runtime to recover.

Pets at home during the day: 78 to 80 degrees. Dogs and cats handle heat better than the internet often claims, but small dogs, seniors, and brachycephalic breeds like bulldogs need the lower end. Never let the setpoint climb above 82 with animals inside.

How Your Home’s Age Changes the Right Setting in Edwardsville

Edwardsville’s housing stock spans everything from 1850s frame houses near downtown and the historic district to 2020s builds in newer subdivisions off Governors Parkway. That range matters for AC settings because the same thermostat number produces different comfort in different envelopes.

Pre-1970 homes typically have single-pane windows, minimal wall insulation, and undersized return ductwork. These houses often need thermostat settings 2 to 3 degrees lower than the DOE baseline to feel comfortable at the same perceived temperature, because the walls and windows radiate heat inward. The high-value fix is upgrading insulation and adding storm windows, not permanently lowering the setpoint.

1970 to 1995 homes vary widely depending on prior owner upgrades. Attic insulation added in the 1990s upgrade cycle helps a lot. Original single-pane windows still in place hurt a lot.

Post-2000 homes typically hold the DOE 78-degree setpoint comfortably when the AC system is properly sized. If a newer home does not, the equipment is likely oversized, undersized, or overdue for ac maintenance.

Newer construction (2015 and later) with modern insulation and dual-pane windows can often push the setpoint to 79 or 80 during the day without loss of comfort, because the envelope keeps the interior temperature stable and the humidity load lower.

Common Mistakes That Waste Money at Any Setpoint

The setpoint number matters less if you are undermining it with habits that force the AC to work harder than it needs to.

Cranking the thermostat to 65 does not cool the house faster. Central AC systems cool at a fixed rate. Setting the thermostat lower just makes the compressor run longer past the point you actually wanted to hit. Set it to the temperature you want and wait.

Closing vents in unused rooms usually backfires. Modern HVAC systems are designed for a balanced airflow. Closing vents raises static pressure in the ductwork, can trigger evaporator coil freeze-ups, and often costs more than any zoning benefit.

Skipping filter changes kills efficiency. A filter that has not been swapped in 90 days can cut airflow enough to raise cooling costs 10 to 15 percent and cause the exact humidity problems described above.

Running the AC with windows cracked. Every open window loses conditioned air and pulls in humid outdoor air the AC then has to remove. The one exception is running whole-house fans at night when outdoor temperatures drop into the 60s, which some Edwardsville homes still have set up from the pre-central-AC era.

Ignoring shade. South- and west-facing windows without blinds or awnings add hundreds of BTUs of load per hour on hot afternoons. Blackout blinds on the sun-facing rooms are a $150 investment that shifts the ideal setpoint 1 to 2 degrees higher.

Ceiling Fans, Blinds, and Other Free Cooling

Ceiling fans do not lower room temperature. They move air across your skin, which increases evaporation and makes you feel roughly 4 degrees cooler than the actual thermostat reading. That is why fans plus a 78-degree thermostat can feel more comfortable than no fans plus a 74-degree thermostat.

The fan-only savings math is significant. If a fan lets you keep the thermostat at 78 instead of 74, that is a 12 to 20 percent reduction in cooling costs across the summer, at the price of running a ceiling fan motor that draws roughly 15 to 90 watts depending on the fan and speed. Always turn ceiling fans off when the room is empty, because a fan cooling nobody is just spending money.

Blackout blinds on west-facing windows, especially bedroom windows facing hot afternoon sun, cut the peak cooling load in those rooms by 30 to 50 percent according to Department of Energy window guidance. Curtains alone help less than blinds mounted inside the window frame with a reflective backing.

Ductless mini splits for a specific hot room (a converted attic bedroom, an addition, a west-facing home office) let you run the main house at a higher setpoint while giving one room aggressive cooling. This is often the smart fix for older Edwardsville homes with one impossible-to-cool second-floor bedroom.

When to Stop Guessing and Get the System Checked

The right AC setting is meaningless if the equipment cannot actually deliver conditioned air the way it was designed to. Three symptoms tell you the setpoint conversation is really a maintenance conversation.

If the house does not reach the setpoint even with the AC running for hours, the system has lost capacity somewhere: refrigerant charge, coil fouling, airflow restriction, or compressor wear. If the setpoint is 74 but the humidity is stuck at 65 percent, the system is not running long enough to dehumidify. If the energy bill has jumped year over year with no change in setpoint or usage, something inside the equipment is drawing more current than it should.

A spring ac maintenance visit takes about an hour, catches most of these problems before summer heat exposes them, and typically pays for itself in the first month’s utility savings once the coil, refrigerant charge, blower motor, and airflow are all back inside spec.

Setting Your AC Right for Every Edwardsville Summer

The best answer to what temperature should I have my AC set at in Edwardsville is not a single number. It is a schedule that respects how you actually use your house, a humidity target you can measure with a $15 tool, and a maintenance routine that keeps the equipment able to deliver whatever setpoint you pick. 

A household that follows the DOE 78-degree baseline during the day, drops to 72 to 74 in the main house overnight with a bedroom fan doing the rest, keeps indoor humidity between 45 and 55 percent, and does one spring tune-up will land at the comfortable low end of Edwardsville summer cooling bills without giving anything up on comfort.

For homes where the setpoint conversation keeps ending in an uncomfortable house or a bad electric bill, the underlying issue is almost always equipment or airflow, not the number on the thermostat. B & W Heating & Cooling has been dialing in AC systems across Edwardsville, Glen Carbon, Maryville, Troy, and Collinsville for decades. 

Call B & W Heating & Cooling at (618) 254-0645 to book a maintenance visit, get the actual humidity and airflow numbers measured for your specific setup, and stop guessing at what your thermostat should read.

FAQ

What temperature should I set my AC to save money in Edwardsville? 

The DOE-recommended baseline for cost savings is 78 degrees Fahrenheit when you are home and awake, 82 degrees when you are asleep, and 85 degrees when you are away for the day. Every degree lower than 78 adds roughly 3 to 5 percent to the cooling portion of your Ameren bill, so pick the setpoint deliberately based on how much comfort you are willing to trade for savings.

Is 72 degrees too cold for my AC in summer in Edwardsville? 

Not physically, but it is expensive. Holding a house at 72 versus 78 costs approximately 18 to 30 percent more on the cooling side of your electric bill through the peak Edwardsville summer months. Ceiling fans, blackout blinds on west-facing windows, and a properly dehumidified home can often deliver the same perceived comfort at 76 to 78.

What is the ideal bedroom temperature for sleep in Edwardsville summers? 

Sleep researchers put the ideal bedroom temperature at 60 to 68 degrees Fahrenheit for quality sleep. Running the whole house that cold is impractical and expensive, so the practical approach is a main-house setpoint of 72 to 74 overnight with a bedroom ceiling fan or targeted cooling pulling the sleeping space down another 4 to 6 degrees.

Why does my house feel humid even when the AC is running? 

The AC is likely oversized, short-cycling, or has a fouled coil that is preventing proper moisture removal. Indoor humidity above 60 percent in a house with a running AC is a service call, not a setpoint problem. The EPA recommends indoor humidity in the 40 to 60 percent range for both comfort and mold prevention.

Can I turn my AC off during the day when nobody is home in Edwardsville? 

Turning it off completely on a hot summer day is not recommended. Indoor humidity spikes fast, and the AC has to run for hours to recover both temperature and moisture, which usually costs more than just leaving it set to 82 or 85 while you are away. The DOE guideline of 85 degrees away is the sweet spot for saving money without paying a heavy recovery cost.

How much should ceiling fans change my AC setpoint in Edwardsville? 

Ceiling fans typically make a room feel 4 degrees cooler than the actual temperature by moving air across your skin. That means a 78-degree thermostat with a fan running feels similar to a 74-degree thermostat without one, which translates to 12 to 20 percent savings on the cooling portion of your bill over an Edwardsville summer.