What to set the thermostat to in the summer? This best temperature for AC is an age-old question. Is 72 degrees a good temperature for air conditioning? Or should you set the air conditioner temperature to 75°F? Even 78°F? There is no absolutely correct answer on how to set AC temperature for cooling in the summer months.
According to a Wikipedia article on room temperature, human beings describe temperature between 75°F and 79°F as ‘comfortably cool’. Other sources like World Health Organization cite comfortable indoor temperature levels to be between 64°F and 75°F. So, there is quite a lot of variability on what is the correct temperature to set the air conditioner in the summer.
Weird thing we do: In the summer, we set the AC thermostat to 72°F. In the winter, we set the furnace thermostat to 75°F. These two temperatures feel the same. This is because of humidity levels; as we will explain further on, humidity plays a key role when setting thermostat temperature.
Factoring in humidity, we can answer the question ‘What temperature should I set my air conditioner in summer?’ in a correct way. We will look into the key factors that determine if you should set the temperature to 72°F, 74°F, 75°F, 76°F, or 78°F to answer what is a good temperature for air conditioning.
Namely, when figuring out what temperature to set the air conditioner in the summer, you are looking at a compromise between 3 key things. These are:
- Air conditioner energy expenditure and wear-and-tear. If you set the thermostat to 72 degrees, the air conditioner running costs will be much higher than if you run it at 78 degrees. The US Department of Energy (DOE) specifically points out that the best AC temperature for energy saving is 78°F (ideal for the a electric bill). Higher temperature also means that the AC won’t have to work as hard and will probably last longer.
- Your comfort levels. If you can handle 78°F, you should set the air conditioner thermostat to that temperature. However, we much prefer to live in homes that are closer to 72°F. What is a good compromise between these two temperatures? It actually depends a lot on humidity levels. Further on, we will see how humidity levels tend to be the determining factors when deciding what to set the thermostat to in the summer.
- Decay of home and furniture. This is usually the most overlooked aspect of the whole what temperature to set the air conditioner in the summer. In the summer, we have double risk factors; high temperatures and high humidity levels. Setting air conditioner temperature too high possess a potential threat to our house; mold growth, wood decay, temperature-sensible glues in furniture, and so on, can all be affected.
As you can see, what temperature to set an air conditioner in the summer is a balance primarily between AC running costs and comfort levels. On top of that, it is very important to understand that humidity also plays a crucial role here since we perceive for example 75°F differently at different indoor humidity levels, and all air conditioners reduce humidity levels as well as the temperature.
We will look into humidity levels that are closely connected with how we perceive the indoor temperature. At high humidity levels, it feels hotter and we sweat a lot, and visa versa.
At the end of the article, we will factor in all these factors and summarize exactly what temperature to set the thermostat in the summer in your area (general AC thermostat setting recommendations state-by-state).
What Should AC Be Set At Depends On Humidity Levels
The main thing we need to understand when setting an AC thermostat is the effect of humidity on our comfort levels. Humidity levels explain why we generally set the thermostat temperature lower in the summer than in the winter.
Here’s the thing:
At high humidity levels, the same temperature feels hotter. Example: 74°F feels like 71°F at 20% humidity levels. If the humidity levels would be much higher – say 80% – 74°F feels like 77°F. That’s a 6-degree difference in how our bodies perceive the thermostat temperature due to different humidity levels.
This ‘Human Temperature’ chart details how different thermostat temperatures are perceived depending on humidity levels:
This chart gives us an insight into how we can think about what temp should air conditioner be set at.
At a 75°F thermostat setting, our bodies will perceive this temperature as:
- 70°F at 10% humidity levels.
- 72°F at 20% humidity levels.
- 73°F at 30% humidity levels.
- 74°F at 40% humidity levels.
- 75°F at 50% humidity levels.
- 76°F at 60% humidity levels.
- 77°F at 70% humidity levels.
- 78°F at 80% humidity levels.
- 79°F at 90% humidity levels.
- 80°F at 100% humidity levels.
In short, at very low humidity levels, a 75°F AC setting will feel like 70°F. At very high humidity levels, the same 75°F air conditioner setting will feel like 80°F.
This is because air with higher humidity levels contains more energy, and we feel that energy as a higher temperature. This phenomenon is, in the science community, based on the Mollier diagram.
For homeowners with ceiling fan: Note that a ceiling fan does not cool the air but it can lower our perception of temperature by as much as 4 degrees, according to the DOE:
If you use air conditioning to cool your home, a ceiling fan will allow you to raise the thermostat setting about 4°F with no reduction in comfort. (DOE on cooling ceiling fans)
Now, how does this affect what to set the thermostat to in the summer:
Why Do We Set Thermostats Lower In The Summer Than In The Winter?
DOE recommends setting the thermostat to 78°F in the summer and 68°F in the winter. This is, obviously, to minimize our energy bills. However, we usually do the opposite: We set the AC thermostat to 72°F in the summer and the furnace thermostat to 75°F in the winter. Why is that?
Exactly: Humidity levels.
In the winter, we have low humidity levels (usually below 40%). That’s why we use humidifiers in the winter. In the summer, however, we have high humidity levels (usually above 40%). That’s why we use dehumidifiers (and air conditioners) in the summer.
That means that the same thermostat setting (let’s say 74°F) feels hotter than 74°F in the summer and colder than 74°F in the winter. You can read more about how humidity affects our perception of temperature in detail here.
What is important to understand here is that air conditioners do two things:
- Lower air temperature. This is quite obvious to everybody.
- Lower humidity levels. This is less obvious; by lowering humidity levels, our perception of temperature is cooler.
Given this insight into humidity levels, let’s look at when it makes sense to set the temperature to 72°F, 74°F, 75°F, 76°F, or 78°F in the summer:
78°F Setting: Best AC Temperature For Energy Saving
If you want to minimize your cooling costs, setting the AC thermostat to 78°F is ideal, according to DOE. On average, you are saving about 3% on cooling costs for every 1-degree increase in the AC thermostat set temperature.
That means that setting the air conditioner to 78°F instead of 75°F will save you about 9% on cooling costs.
That’s all well if you can handle 78°F indoor temperature. As we have explained above, is 78°F a good temperature for air conditioning depends on what indoor humidity we have.
Namely, a 78°F AC thermostat setting will feel like:
- 76°F at 30% humidity levels.
- 77°F at 40% humidity levels.
- 78°F at 50% humidity levels.
- 79°F at 60% humidity levels.
- 80°F at 70% humidity levels.
- 82°F at 80% humidity levels.
Now, if you live in drier climates like Arizona, New Mexico, or even the western part of Texas or the eastern part of California, you can set the AC thermostat to 78°F. That’s because you probably have below 50% humidity levels in the summer at 78°F AC setting will not feel higher than 78°F.
However, if you live in the northern US, like New York, Illinois, or Florida, you are experiencing high 70% or more humidity levels. At 70% humidity, 78°F AC thermostat will feel like 80°F. This is not a temperature many people are comfortable living at.
In short, if you live in dry climates, you can potentially set the AC thermostat to 78°F; it is the best AC temperature for energy savings. Even in dry climates, homeowners prefer to set thermostats to lower temperatures (75°F, for example). If you live in a damp part of the US, you will definitely sweat if you set the AC temperature to 78°F.
Let’s look at lower AC thermostat settings:
Is 75°F A Good Temperature For Air Conditioning?
As we have noted above, we perceive temperatures between 75°F and 79°F as ‘comfortably cool’. That means that setting AC to 75°F is a good temperature for air conditioning, right?
Well, mostly right, but we do have to take into account the humidity levels. Namely, if the humidity levels at between 50% and 90%, we will experience temperatures between 75°F and 79°F; comfortably cool temperatures.
Because a large part of the US has humidity levels between 50% and 90%, the 75°F is the temperature most Americans should set their AC thermostat to.
If you live in drier parts of the US, however, 75°F might actually feel too cool. At 30% humidity levels, 75°F feels like 73°F. According to some sources, 73°F is a bit chilling. World Health Organization puts comfortable indoor levels between 64°F and 75°F.
The best thing to do is feel what temperature you feel comfortable at.
Let’s check what happens if we set temperature levels to 72°F:
Is 72°F A Good Temperature For Air Conditioning?
Many air conditioning manufacturers will put ’72°F’ on the photos of their air conditioners. That’s usually just marketing; look at how cold our AC unit can go.
But is 72°F a good temperature for air conditioning? In many cases, not really. 72°F is usually a too low setting for air conditioners which results in two things:
- Your cooling bills will likely skyrocket if you set AC to 72°F instead of setting it to 78°F, for example.
- It might feel chilling indoors.
If we check what temperature we will actually feel (humidity-dependent) if we set AC thermostat to 72°F is the summer, we get these temperatures:
- 69°F at 30% humidity.
- 70°F at 40% humidity.
- 71°F at 50% humidity.
- 72°F at 60% humidity.
- 73°F at 70% humidity.
- 75°F at 80% humidity.
As you can see, 72°F feels like below 75°F if the humidity is below 80%. That means that in most parts, 72°F is a too low temperature for air conditioning.
However, if you live in very humid areas like Florida, setting the AC thermostat to 72°F does make sense. If you have 80% humidity levels, 72°F will actually feel like 75°F.
Bottomline On What Should You Set Thermostat To
As we have seen, how many degrees you should set on your thermostat is a compromise between cooling expenses and comfortability levels.
We know that cooling expenses increase by about 3% for every 1 degree we lower our thermostats.
Comfortability levels – how we perceive temperature – are strongly connected with humidity levels. At higher humidity levels, it feels hotter. Because we have different humidity levels in the US, the correct thermostat setting in the summer depends on location.
Here is the summary of what AC thermostats should be set at (general humidity-accounted recommendations):
- Set the AC thermostat to 78°F for energy savings in areas with low humidity levels (below 60%). This is the best AC setting for the eastern part of Texas, Nevada, dry parts of California, Arizona, New Mexico, and so on.
- Set the AC thermostat to 75°F in most areas with humidity levels between 50% and 90%. This includes the majority of US states; check the humidity map above for states with humidity levels between 50% and 90%.
- Set the AC thermostat to 72°F only in very damp areas like Florida. 72°F is quite a power-hungry setting that should be used at very high humidity levels.
With all of this considered, we hope that you now have a good understanding on what temperature to set the air conditioner in the summer. If you have any questions, or would like to describe your situation, or share an option, you can use the comment section below and we’ll try to help you out.
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