What Temperature Should You Set Your Air Conditioning To?

As warm weather sets in, it’s only a matter of time before you turn on your air conditioner. Whether you’ve got central air, window units or ductless panels, cooling off is key during the summer months. 

However, as comfortable as it will make your home, it will also be costly. On average, it costs between a quarter and thirty-five cents per hour to cool a 36-square-foot room. An air conditioner in a larger room, around 50 square feet, it’s nearly a dollar an hour. 

One way to keep your energy bills from getting too high is to set your air conditioner to a reasonable temperature. Not using too much energy means not paying more in energy bills. 

So you want to keep that expense low. But, you also don’t want to be too hot. After all, what’s the point of running the a/c if you’re still sweating? The trick is to find a sweet spot: A temperature that feels right to you but also doesn’t cost too much to maintain. 

There are a few steps you can take to find the most reasonable temperature to set your air conditioner at

. Here’s how to do it...

Start by setting your air conditioner high

When trying to find the most reasonable setting for your air conditioner, you have to start somewhere. And, the best spot to do it at is 78 degrees Fahrenheit. 

According to Energy Star, it’s an ideal temperature. 78 degrees keeps you fairly cool and comfortable during the day. It also shouldn't make your electric bill skyrocket. 

Start with your thermostat at 78. If that feels ok, increase it by one degree. Find out just how warm you can go and still feel comfortable. Remember, the higher the temp, the lower the bills in the summer. 

Or, if 78 is already too hot, that’s fine too. Just start going the other way. Lower the temp one degree at a time. Try to keep it as high as you can. 

Just remember, however, that each time you lower it, you’re adding a little more to your bill. Going back to Energy Star, look at it this way: If you dial your thermostat back seven to 10 degrees for eight hours a day, you can save 10 percent every year on your energy bills. 

Next, figure the average American spends around $1,100 annually in energy costs. Now imagine moving your thermostat from 68 to 78 degrees in the summer. And, in the winter, you make similar adjustments. That could mean more than $100 in savings every year. 

Adjust the air conditioning with ceiling fans

The trick here is ceiling fans. Running them while you’re in the house won’t actually cool down any of the rooms. What they will do, however, is move around the air. 

When you’re running an air conditioner, you’re pumping cool air into your house. A fan helps circulate that cold air. So, it doesn’t actually lower the temperature. But, it does help your air conditioner do its job better. 

Those fans can make a bigger difference than you might think. According to the United States Department of Energy, a ceiling fan can make a room feel four degrees cooler. 

Now, let’s go

back to

the

78-degree

rule. Maybe that’s too warm, but you can do 74 degrees. Turn on your fans and keep your thermostat at the higher temp. It’ll feel cooler than it reads. 

There are, however, two things to remember here. First, make sure the fans are running counter-clockwise. You want them to blow the air straight down. If you set them clockwise in the winter to help keep things warm, turn them back now. 

Secondly, turn off the fans if you’re not in going to be in that room for a while. Remember, the fan isn’t creating the cool air. The air conditioner is. 

If you turned off the a/c, then yes — it would take more time and energy to turn it back on and begin cooling the room again. But the fan is just moving the cooler air around. So, you can let the room feel a little warmer when you're not in it. Then, turn the fan back on when you’re there.

Change your thermostat setting for different times of day

Finally, you can set your thermostat to different temperatures at different times of the day. That’s especially so if you keep a regular schedule are out of the house for hours at a time. And, most people don’t need to keep things quite as cool when they’re sleeping as they do when they’re awake. 

Going back once again to the 78-degree rule-of-thumb: That’s for when you are awake and in the house. In the evening, try setting the thermostat four degrees warmer. With that change, you’ll save a little bit money. But, you won’t be sweltering and unable to sleep. And, again, remember that you can use a ceiling fan to cool things down a little more. 

And, set it at least seven degrees higher when you’re leaving for the day. This strikes a good balance. You’ll lower your energy bills, especially if you’re gone most of the day. But, the house won’t get so warm that the thermostat has to work extra hard to cool it back down when you get home. 

It can be a lot to remember the exact settings and times. And, it’s an extra step in your schedule to make those changes. Fortunately, there are plenty of ways to make it easier. 

For instance, you can consider a smart thermostat. These are programmable, so you can set them to change by themselves when you want them to. But, they go even further. 

When the weather is warmer in spring, summer, and early autumn, you may be wondering if your central air conditioning is running efficiently. Is the air coming out of the AC as cool as it is supposed to be?

Below, we look at what temperature the air blowing from your AC system should be, and how some components of your air conditioning work. Lastly, we’ll troubleshoot some common issues if the air appears to be blowing too hot, and possible fixes.

How Cold Should the Air Coming From Your Air Conditioner Be?

Air conditioners do not create “cold” air, they remove heat energy from existing air and recirculate it in an environment.

An ideal temperature differential between air coming into to be cooled, and the air being blown out is 14° to 20° F.

The temperature difference between return and supply air is known as the evaporator Delta T.

What Is Supply and Return Air?

When your central air conditioner is in cooling mode, warm air is pulled into large grilles placed strategically in the home. This is return air.

Return air runs along an evaporator coil, where heat energy is absorbed by refrigerant in the coil. This heat energy is exchanged in the outdoor condenser/compressor.

The now cooled air is blown through supply registers or vents, sometimes placed is the ceilings or walls of the home. This is supply air.

An easy way to remember which air is which: the air that has yet to be conditioned is returning to the heat exchanger or evaporator. The conditioned air is supplied to the home.

Measuring the Air Temperature Differential in Your Home AC System

To measure the differential temperature, or Delta T, of your air conditioning unit, first run the AC for at least fifteen minutes. Then, using an infrared thermometer, measure the temperature of the air coming from the supply register nearest the evaporator coil for five minutes. Next, measure the temperature of the air at an air return grille for five minutes. Last, subtract the supply air temperature from the return air temperature. This should be between 14 and 20 degrees Fahrenheit.

What if the Temperature Differential Isn’t Hitting the Target?

If you are seeing a different temperature gap on different supply vents, it is possible there is a leak or a blockage in your ductwork. When one or more vents are blowing warm air, but others are blowing cool air, it is likely that there is a rupture in the ductwork causing cool air to escape.

If all the supply vents are blowing air that is too warm, it could be a few different issues.

It is possible that you have dirty air filters that are causing inefficient cooling. Replace the filters and see if that solves the problem.

Another common issues is that the refrigerant is low. This facilitates the heat exchange, as heat energy is absorbed into the refrigerant, and dispersed outdoors. In the winter, this process works in reverse. These two issues are relatively easy to fix.

Now, it can also be possible that you have major leaks in your ductwork, in the attic, walls, or under the house—depending on how your ductwork was set up. If you have notice a sharp increase in your energy bills, that stays consistently high, this might be the root cause. This has the potential to be a more complicated fix.

One other possible culprit for warm air blowing from your AC might be a dirty evaporator coil. This is where heat is exchanged.

If you are unsure of why your air conditioner is working inefficiently, call a professional HVAC contractor.

How to Keep Your Home Cool in Warmer Months

If you keep in mind that your air conditioner will consistently push our air that is 14 to 20 degrees cooler than the air coming in, you can strategize how to keep your home cool when the mornings and afternoons are warm.

It is easiest to keep the temperature in a comfortable range instead of trying to quickly decrease the temperature in the middle of the day. First, use shading and other techniques to keep the air inside your home cool. Here are some ideas for keeping your home cool without AC.

Next, if you are using a smart thermometer, keep the “away” temperature within 5 degrees of your target temperature. It will take about an hour for your AC system to hit the target temperature when you get home. Moving the thermostat to a lower temperature when you get home from in the evening doesn’t make the air conditioner cool the home any faster. The air coming in the return vents still has to remove heat, and the cooler air must circulate through the supply registers in the rooms of your home.

If You Need Help With AC Repair in the South Bay / San Jose

Ventwerx HVAC can help homeowners AC repair, air duct cleaning and inspection, ductless HVAC, and any other residential AC repair. We serve the San Jose area, as well as Morgan Hill and Gilroy. We are licensed and bonded, and have served the South Bay and Central Coast since 2007.

If you need air conditioning repair or AC replacement, fill out a service request, or call (408) 422-2987 in San Jose or (408) 710-9595 in Morgan Hill.