When the dog days of summer are upon us, you may be wondering how long it should run before shutting down or if its harmful to run it for an extended period of time?
As a licensed HVAC contractor, I’ve lost count of how many times I’ve been asked this question.
Air conditioners are designed to run continuously and can run all day without stopping.
When the heat is oppressive and unforgiving during an extreme heat wave, it’s exceedingly common for an air conditioner to run all day long.
However, if your A/C runs all the time on mildly warm days, then it may be undersized or have some other issues like a dirty filter.
During moderate heat waves a typical run cycle is 15-20 minutes long, usually 2-3 times per hour. The hotter it is outside, the longer your AC will run to transfer the heat from your home outside.
7 Factors of AC’s Running Continuously
Several equipment and mechanical related issues can affect how long your AC can run continuously.
- Properly Sized Equipment
- Equipment Age
- Poor Airflow
- Dirty Air Filter
- Dirty Condenser Coil
- High Temperature and Humidity
- Insulation and Sunlight
Factor #1: Properly Sized Equipment
Proper AC size is crucial for both comfort and efficiency.
Air conditioners are sized by the “ton.” One ton of cooling is equivalent to 12,000 BTU/hr. Heat load calculations are required to size air conditioners properly and take into account:
- The size of each room
- The amount of insulation in the walls and attic
- The material the home’s built of
- The amount of sunlight
- How many doors and windows
All of these figures (and possibly more) have to be known to properly size an air conditioner so that it can efficiently cool the space it’s designed for.
If your AC is undersized, it will struggle to maintain comfortable temperatures and will run continuously even on moderately warm days.
During extreme heat, it won’t keep up at all. Your air conditioner runs all day and the temperature in the house keeps climbing.
If your AC is oversized, it won’t have any issue reaching your set temperature regardless of how hot it is outside. It will run in short cycles and struggle to remove the humidity from the air.
The excessive wear and tear on the compressor will inevitably reduce the equipment’s life expectancy.
Read Also >> Why Is My AC Window Unit Leaking Water?
Factor #2: Equipment Age
Like all mechanical equipment, your AC has an expected lifespan.
Parts and equipment wear out overtime and have to be replaced. The average life expectancy of a modern AC is 15-20 years, but depends heavily on where you live and how well your equipment has been maintained.
Coastal areas usually only get 8-12 years for an air conditioner because of the salty conditions.
Southern climates typically use air conditioners more of the year increasing wear and tear which decreases life expectancy, while northern climates use them less frequently allowing them to last longer.
The older an air conditioner is, the more likely it is to have problems. It may have sprung a leak or it has coil issues preventing proper heat transfer.
These types of problems will cause the compressor to run all the time and prevent proper cooling.
Factor #3: Poor Airflow
Lack of airflow at the indoor and outdoor units can create a scenario where your air conditioner runs all day.
Factor #4: Dirty Air Filter
Dirty air filters reduce airflow at the indoor evaporator coil. Poor airflow will cause the coil to get very cold and freeze the accumulated moisture on the coil fins.
Once the coil freezes it can no longer remove heat from your home and then your AC unit is running all day without cooling the house down.
If you find yourself with a frozen coil, I invite you to read our article on how do you unfreeze an air conditioner?
Regularly replacing your air filter will prevent this from happening.
Factor #5: Dirty Condenser Coil
A dirty condenser coil prevents airflow through the outdoor unit. This is where the heat from the house is exchanged to the outdoor air.
If it is not properly removed, you’ll have excessively high head pressure which causes the compressor to work significantly harder, increasing your electric bill.
If you notice your ac is running for 12 hours a day, this may be the cause.
Washing your condenser coil with a garden hose to remove significant debris will help tremendously.
Chemical cleaners may be necessary to thoroughly clean indoor and outdoor coils.
If you aren’t sure what type of cleaner to use on your coil, check out our article on the best cleaner for AC coils.
Factor #6: High Temperature and Humidity
Excessive heat and humidity will almost always cause your air conditioner to run continuously.
The bigger the difference in temperature between your indoor set point and the outdoor temperature, the harder and longer your AC will run. I also encourage you to read our guide on what is a good temperature for AC in summer.
Keeping your thermostat set point as high as comfortably possible will help your AC run as efficiently as possible.
Factor #7: Insulation and Sunlight
Poorly insulated homes allow heat to infiltrate through the walls and ceiling increasing the temperature of your home.
Since it’s the air conditioners job to remove heat from the house, additional heat from the walls and attic cause it to work overtime to keep you cool.
Insulation is one of the best investments you should consider when trying to increase your heating and cooling efficiency.
Large windows or an abundance of windows allow significant sunlight to enter a living space.
The majority of sunlight that enters through the window becomes heat and increases the load on your air conditioner, potentially causing your AC to run all day.
Window coverings can help reduce the amount of extra heat added from sunlight, increasing efficiency and decreasing utility bills.
Takes Less Energy For A/C To Keep Running
It may seem counterintuitive that a system running continuously is more efficient than a unit that cycles off frequently, but that is the case with air conditioning.
The compressor in the outdoor unit, the component that “pumps” the refrigerant, uses the most power on startup.
It takes more energy to start the compressor than it does to keep it running.
Short Cycles Reduce Life Expectancy
A system that has short cycles, kicking on and off every 5 minutes or so, will consume large amounts of power and will greatly reduce the life expectancy of the equipment.
The shorter run cycles also prevent proper dehumidification, creating an uncomfortable environment and encouraging mold growth.
Higher Efficiency Allows AC to Stay On Longer
The higher the rating, the more efficiently the air conditioner can transfer heat. Most of the time these higher efficiency units are multi stage or have modulating compressors.
This allows the unit to stay on longer at lower capacity and lower energy usage while keeping consistent comfortable temperatures in your home.
An air conditioner running continuously with this type of system is to be expected and generally is more efficient to operate.
SEER Ratings
All air conditioners have an efficiency rating also known as SEER.
SEER stands for seasonal energy efficiency ratio and represents how much energy the unit requires over the course of one year.
SEER2 is the updated version of this that started January 1, 2023 and includes a blower testing procedure that more accurately depicts real world conditions to get more precise efficiency ratings.
RELATED: Why Is My A/C Condenser Leaking?
Maintenance Will Extend Life of HVAC
Preventative maintenance is encouraged to ensure optimal AC performance for as long as possible.
Regularly replacing air filters and keeping coils clean can make a world of difference in how your air conditioner operates. It can significantly extend the life of your equipment.
Pick A High SEER Rating
When the time does come to look at a replacement, consider a higher SEER or SEER2 rating.
Look at the equipment capacity and staging and ask questions. Bigger isn’t always better, at least not with AC.
You want an air conditioner that isn’t too big or too small. It has to be just right for your home and the amount of insulation you have. Make sure the installing contractor is thorough when sizing your equipment.
READ ALSO: How To Fix Bad Air Conditioner Smells?
Final Thoughts
It may seem like something isn’t right if your AC runs continuously or seems to be struggling.
That may not necessarily be true. If you have your thermostat set low and the outdoor temperature is significantly higher than that, don’t be surprised if your air conditioner runs all day.
It’s most likely running exactly as it should.
On the other hand, if the temperature in the house continues to climb or it can’t keep up on a mild day, you may have something to be concerned with. If that’s the case, start with your filter and check your coils.
It’s usually best to call a professional to check things out as well to make sure everything is working as efficiently as possible.
Doing so can help extend your equipment’s lifespan and give you peace of mind that you’ll be comfortable all summer long.
Frequently Asked Questions
Should My A/C Be Running All The Time?
Yes, it’s okay for your AC to run continuously on hot days. Modern air conditioners are designed to run 24 hours a day.
What Should Be The Max Running Time?
There is no length of time that is too long for an air conditioner to run. If your system is running constantly and not cooling, it’s best to shut it down and have it looked at by a professional.
On A 110°F Day What Temperature Should My House Be?
If it’s 110 degrees outside, I recommend setting your thermostat at 78°F. Most air conditioners can only cool between 20-25°F degrees below the outdoor temperature, so your unit may struggle to maintain with outdoor temps that high.
Should My A/C Be Struggling With Extreme Heat?
In extreme heat it is not out of the ordinary for an AC to struggle to maintain temperature, but on standard hot days it shouldn’t be an issue.
It may run continuously, but it should keep up.
What Should Be The Average Cooling Time From 80°F to 72°F?
On average it should take about 3 hours to cool from 80°F to 72°F, but this depends on several variables.
Outdoor temperature, equipment size and efficiency, and home size are a few factors that have to be considered and can change the length of time.
Will It Get Damaged If Constantly On?
Nothing major happens if your AC is running excessively.
Air conditioners are designed to run for long periods of time. Other than normal wear and tear, there’s nothing to be concerned with.
