Every summer, our customer service team fields countless calls from customers asking why their air conditioner isn’t getting the house as cool as they’d like it to be, especially on the hottest days.
I have the temperature set for 72 but no matter how many hours it runs, my air conditioner won’t get the house cooler than 78.
What’s going on?
Your air conditioner is much different than your furnace
In the middle of winter, you can bump up the thermostat several degrees and within a reasonable amount of time a well-functioning heating system will warm the house to your preferred temperature, even when it’s really cold outside.
Not so with an air conditioning system.
While a furnace can keep your house at a steady 68 degrees all winter—even if outdoor temperatures drop into the 20s or 30s—your air conditioner is only designed to cool to within about 15 or 20 degrees of the outside temperature.
That means that on really hot days, your air conditioner may not seem to be “keeping up.”
We know this can be frustrating, especially since your air conditioning system was a big investment.
Here’s why your system may not seem to be cooling as well on the hottest days.
Air conditioners are sized according to your region’s weather patterns
For every region, there are numbers and codes that dictate how cooling systems are designed in order to function optimally.
One of the most important is the 1% design temperature. In Olympia, the outside temperature reaches above 85 degrees only 1% of the hours in a year, based on a 30-year average. So for Olympia, the 1% design temperature is 85. This means that all systems in this area, to be most effective and efficient, are designed to function optimally when the temperature outside is 85 degrees or lower.
Of course this means that when temperatures are higher outside, air conditioning systems in this area may not be able to cool to your desired temperature—or it will take longer for them to do so.
Can’t I just get a larger air conditioning system anyway?
No. And here’s why.
All air conditioning systems work best when they run consistently. If you live in a milder climate, like the Pacific Northwest, an oversized system won’t run consistently, which means it will be inefficient and less effective overall.
Problems that occur with oversized systems include:
Your system turns on and off more often. Short cycles occur when the system cools off the area around the thermostat before cool air can be distributed to the rest of the house, prompting it to shut off before the entire house is cool. A properly sized unit will cycle longer, ensuring that the whole house is cool.
Your house gets humid. The “conditioning” part of air conditioning is the system’s ability to remove humidity from the air—a major factor when it comes to comfort. An oversized system that’s running in short bursts doesn’t have enough time to properly pull moisture from the air, making your home feel sticky. A cycle of at least 20 minutes is better able to dehumidify the air; oversized systems tend to cycle for only 8 to 10 minutes at a time. Keep in mind that humid air is not only uncomfortable, it can also lead to mold problems in your home.
Your energy bills are higher. Because they cycle so often, oversized systems are inefficient—and your energy bills may reflect this. Air conditioning systems that are sized for your climate will run the optimal amount of time, saving you money.
Couldn’t there actually be something wrong with my air conditioner?
There could be. If your air conditioner is sized properly for your home and the temperature outside isn’t too high and your air conditioner still isn’t cooling, there could be other factors at play.
Infrastructure issues such as insulation and window size and placement could be working against your air conditioner. Functional issues, such as dirty filters or coils, refrigerant levels, an overheating compressor, or even leaking air ducts could be factors.
If you think it’s your system and not the spiking temperature outside, it may be time to have a service technician out to check your system.