Dirty Air Filter When this happens, your system has less air to condition. For example, your thermostat may say 74 but the temperature won't get below 80 degrees. A dirty air filter could also freeze your evaporator coil. When it freezes, it'll turn into a block of ice and stops any cool air from going into your home.
Your AC might not cool properly due to thermostat issues, an undersized unit, or extremely high outdoor temps—so check those first. Keep an eye on airflow—replace clogged filters every 3 months, and make sure vents and ducts aren't blocked for efficient cooling.
It's called thermal inertia, the tendency to stay the same temperature until heat is either added or removed. Eventually, the inside temperature will approach the outside temperature, whether or not it started warmer or cooler, absent an active cooling or heating system.
A refrigerant leak
Your refrigerant is the special chemical that cools the air inside your home. So, if there's a leak and your system eventually becomes low on refrigerant, your AC will be extremely limited in how much cooling it can provide.
The recommended thermostat setting for summer is 72 to 78 degrees. On long, hot summer days it's tempting to push your air conditioning to the max — but be careful. Heating and cooling typically makes up the largest energy expenditures in a household.
On average, an air conditioner running in good condition should take about 15-20 minutes to drop the temperature by 1 degree in a standard-sized room. However, factors like outside temperature, unit size, and insulation quality can affect this timing.
The Ideal AC Temperature
Between 74-77 degrees F (23-25 degrees C). This will limit the strain on your cooling system, keep energy bills reasonable, and help prevent the coils from freezing.
Air conditioners make homes more comfortable on hot and humid days. So, it can be frustrating when the AC is not cooling below 75 degrees, even if it has been running for hours. Many factors can cause this issue, including clogged filters, refrigerant leaks and the wrong unit size.
For many of us, 70 degrees is the ideal indoor temperature, but when it is close to 100 degrees outside, your AC unit will be working quite hard to meet these expectations. Consider setting your thermostat at 75 degrees to 80 degrees in your home if the outside temperature is approaching triple digits.
Clean your Air Filters, Vents, and Ducts – A clogged air filter will struggle to meet the thermostat's set temperature since the dirt and debris buildup prevents air from circulating through the vents. And as airflow into living spaces drops, so do comfort levels.
“The consensus among most scientists is that anything higher than 75 or 80 is bad for sleep and potentially detrimental to health,” Baniassadi said. Heat affects sleep because the body signals the brain that it's time to fall asleep by lowering its core temperature. Sleeping in a hot room makes this difficult.
Your house and attic insulation can wear down over time. Your house also may have hidden attics that aren't properly insulated or uninsulated garage walls that are attached to your home, and this can cause problems with heat escape, unwanted airflow, and drafts. Your ductwork has problems.
If the temperature is set to 74°F but the thermometer shows 78°F, you will have to recalibrate the thermostat to account for this 4-degree deviation. Even with older AC units or furnaces, you might have to recalibrate your thermostat from time to time.
To fix an AC not blowing cool air, ensure the thermostat is set to "cool" mode and the temperature is set lower than the current room temperature. Inspect the air filter as a dirty filter can restrict airflow. Ensure the condenser coils are clean and free of debris. Make sure vents are open and unobstructed.
If your air conditioner isn't keeping up with the heat, your air filter may be to blame. A dirty air filter can obstruct the airflow path through the unit. Using a dirty air filter can also cause less energy efficiency and more costly utility bills.
The Temperature Outside
Most central air conditioners can cool a moderate-sized (3 to 4 bedroom) home by about 5 degrees every 3 hours. This means while it can take no more than a couple hours to lower the temperature to a comfortable range in the fall or autumn, it can take much longer in the summer.
Just because the outdoor temperature is above 100, the Ideal temperature to set your AC unit to doesn't change — it's 78 degrees. Higher temperatures in the home are to be expected when the weather is hotter than usual, but your thermostat can still be set the same as if it were a lower temperature outside.
Yes, it is normal for an air conditioner to run all day when the outside temperature reaches 100 degrees. During such extreme heat, your AC works hard to maintain the right temperature inside your home, which means longer run times and more frequent cooling cycles.
Keeping your home warm in the winter is essential for one's comfort and also to keep pipes from freezing. However, you should be mindful of energy consumption as well. According to the Department of Energy, the optimal temperature setting for homes during freezing weather is 68 °F.
Start by making sure you have it set to your desired temperature and that it's switched to the “cool” setting. Next, double-check your vents to ensure they're open and free from obstructions. If that doesn't work, remove your A/C filter, and inspect it for any dust or discoloration.
In short, the 20-degree rule of air conditioning states that you should always keep your AC unit at no more than 20 degrees lower than the outside temperature. It means that, if the outdoor conditions are at 95 degrees, you should set your thermostat at no less than 75 degrees.
If your home lacks insulation or has air leaks, your AC won't cool your home efficiently. Replacing the air filter or cleaning the coils could be a simple solution. An AC unit that's too small or too old might not be powerful enough to cool your home.
Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it. For those wondering specifically how to reset air conditioner thermostat models, the process is generally the same.
In summer, the best mode for your air conditioner is the "Cool" mode, set to a comfortable temperature around 78°F when you're home. This setting efficiently reduces indoor humidity and maintains a comfortable environment without overworking the AC system.