Why Does My AC Take Forever to Cool the House?

July 06, 2017

Unfortunately, without knowing more about your home, your AC unit and the outdoor temperature, we can’t really tell you why your air conditioner takes forever to cool your house.

But here’s what we can say: If your air conditioner runs all day without cooling your house to the desired temperature, then something’s wrong.

If your AC is slow to cool your home, the problem is likely caused by 1 of these 6 reasons:

  1. It’s very hot outside

  2. A dirty air filter

  3. Refrigerant leaks

  4. Your outside unit is too dirty

  5. Leaky ducts

  6. Your AC is too small or too old (which may require an AC replacement)

In this article, we’ll go into more detail about each of these reasons, how they affect your AC’s ability to cool your home, and what you can do to fix them.

Let’s start with outside temperature...

Reason #1: It’s very hot outside

“Well, duh!”

It’s obvious, but the hotter it is outside, the harder your AC has to work to cool your home to your set temperature.

Your air conditioner was made to keep up with design temperatures, or the range of outdoor temperatures that your city stays between 99% of the year.

Here in Florida, the design temperatures fall between 47° and 93°. So that means that 99% of the year, we don’t see temperatures over 93° F.

Solution: Well, you can’t change the weather. But if everything is working correctly in your AC, that means it’s just one of those 1%, super hot days.

Reason #2: A dirty air filter

If your filter looks like the one on the right, it’s dirty and it’s time to replace it.

Believe it or not, but even a dirty air filter can prevent your AC from cooling your home.

That’s because a dirty filter limits the amount of air that’s pulled back into your system to be cooled. So in a sense, a dirty filter “suffocates” your air conditioner.

Solution: Change your dirty air filter.

Reason #3: Low refrigerant

Refrigerant is an essential part of your AC system. It’s the cooling liquid/gas that absorbs the heat from your home’s air and carries it outside. If your AC is low on refrigerant, it won’t cool your home’s air.

If you have low refrigerant, it’s almost always caused by a refrigerant leak, meaning the lines that carry refrigerant have a hole somewhere.

Solution: Only a professional can and should fix a refrigerant leak. Your technician should fix the leak, then recharge your system with new refrigerant. Contact a certified cooling specialist to fix any refrigerant leaks.

For more information about refrigerant leaks, read our articles:

Reason #4: Your outside unit is too dirty

A dirty outside condenser unit.

The outside condenser unit is the part of your AC system that disperses the heat from your refrigerant into the outside air.

If your outside unit is visibly dirty, or if the condenser coils are really dirty, then your AC will struggle to disperse that heat, which means it will take longer to cool your home.

Solution: Try clearing your outside unit of debris. If you have dirty condenser coils, contact an air conditioning professional to have them clean it for you.

Reason #5: Leaky ducts

Leaky ducts make it harder for your AC to cool your home. Your home can experience 2 types of ductwork leaks:

A diagram of a supply duct leak.

1. A supply duct leak: If your supply ductwork has leaks due to holes or improper connections, then it will take longer for your home to feel cool because you’re losing conditioned air to leaks.

A diagram of a return duct leak.

2. A return duct leak: If your return ductwork has leaks, then your AC system isn’t pulling in enough air from your home to cool, which is why it’s taking longer for your home to feel cool.

Think of a return duct leak like drinking a beverage with a leaky straw: If the straw has holes in it, you can’t drink as much as you could if it didn’t have any holes.

Solution: Have an HVAC professional inspect your ductwork and repair any leaks or holes. According to Energy Star, atypical home loses 20–30% of the air the moves through the ductwork due to leaky ducts.

Reason #6: Your AC is too small or too old

  • Your AC is too small: If your air conditioner is too small for your home, it’ll run constantly, but it won’t cool your home.

  • Your AC is too old: Air conditioners lose efficiency as they get older, which means they’ll generally take longer to cool your home.

For more information about air conditioner age, read our article “How Long Do Central Air Conditioners Last in Florida?

Solution: Contact a professional to inspect your AC system. A technician can perform a Manual J Load Calculation to determine what size your air conditioner should be for your home. The technician will also let you know if your AC unit is too old and discuss options with you about replacing it.

Need a trustworthy AC expert in Florida?

Contact Red Cap Air to schedule an air conditioning repair. We’ll happily answer any questions you may have, and we’ll send one of our trusted technicians to get your AC cooling quickly again.