When you take a look at your thermostat, you may notice that it switches between various modes and settings. All of these modes cause your system to run differently, so it is important to understand what each one does. Our guide will explain how all the different settings work, so you can pick the right one for your needs. If your in the San Diego, CA area and want help with newer technologies like a Smart Thermostat, we got your covered!


Heat is one of the classic thermostat modes found on just about every thermostat model. This mode allows you to control your heater or furnace. To use the Heat mode, you will select your preferred minimum temperature. Any time the air in your home dips below this temperature, the thermostat will turn on the heater.

Most people will use the Heat mode when they are cold in the winter, fall, or spring. Everyone has their own preferred temperature for the Heat mode. Some may set it in the mid-60s range, while others may have their heat in the 70s or even 80s. Whatever your favorite Heat setting, it makes it easy to stay cozy even on cold winter nights.


Cool is the other essential thermostat setting. It works similar to heat, but instead of running the heater, this mode runs the air conditioner. The Cool mode lets you pick your preferred maximum temperature. When the house is cooler than this temperature, the air conditioner will turn off. However, if temperatures rise above your setting, the air conditioner will turn on.

Cool mode is primarily used to avoid overheating in the summer, fall, and spring. People can pick all sorts of temperature settings, with most preferring something ranging from 65 to 75 degrees. In addition to cooling the home, Cool mode also helps to dehumidify the house. As a side effect of running the AC, excess water is removed from the air.


Fan mode is a thermostat mode that turns your HVAC fans on. In Fan mode, the system will run fans to cycle air throughout the home. However, it will not heat or cool air usually. Instead, air will just remain at room temperature. In some thermostat models, Fan mode will completely turn off heat or cool mode.

Some HVAC systems may have Fan mode as a separate mode that operates independently from your temperature settings. With these thermostats, you can leave the fan running all the time, but your air conditioner or heater will still kick on if it is too hot or too cold. This lets you adjust the temperature as needed but keep the fan running when your heater or AC is off.

Fan mode can be useful when you want increased ventilation but are happy with your current temperature. Some people also like that the fan provides a little background noise, helping them to sleep. Though Fan mode will not do much to change the overall feel of your air, your air may smell a little fresher and cleaner. Since your air will get pulled through the filter with each cycle, Fan mode can help remove debris and odors.


Of course, most people will not spend a lot of time using this mode, but it is still worth learning a little about. Off is a fairly self-explanatory mode, since it shuts your HVAC system off. Some thermostats may use other names for off, such as manual.

When you switch into Off mode, your thermostat itself will usually still work. Most models will continue to check temperatures and let you adjust your settings as desired. However, the HVAC system itself will be turned off. Regardless of how hot or cold it gets, your thermostat will not start up your air conditioner. Furthermore, the Off mode will prevent your fan from running.

Off mode is mostly just useful for times when you want to guarantee your HVAC system will not run. For example, if your system is broken and running it will cause further damage, you would want to use the off mode to shut it down. Off mode can also be helpful for temporarily turning off the HVAC to save power when you leave the house. Just remember that extreme temperatures can damage your home or harm pets, so be cautious about using off.


In some thermostats, this mode is also called Auto mode. It is essentially a setting that lets you keep your home in whatever range of temperatures you desire. Unlike a heat setting or a cool setting, this setting can use both your HVAC’s warming and cooling capabilities.

Typically, this setting starts with you selecting your preferred range of temperatures. You tell the thermostat what temperature you want to keep your house warmer than and which temperature you want to keep your home cooler than. The Heat/Cool mode then runs your heater or your air conditioner as needed to stay within your desired range.

The Heat/Cool mode is very useful during summer and fall when the weather varies quite a bit. It lets you stay warm during chilly nights and cool down during hot days. This mode is also convenient because it does not require you to spend a lot of time fiddling with your settings. You just pick your desired setting and let it run.


This mode is not quite as common as others, but it does show up on a few smart thermostats. The Eco mode is simply an energy-saving option. It may go by other names, such as vacant mode or unoccupied mode. Once you set your thermostat to eco mode, it will try to operate in a way that saves you money.

Unlike other modes, Eco mode does not ask you to pick a specific temperature. Some thermostats may ask you to pick an absolute maximum and minimum temperature, while others may skip this step. Once you are in Eco mode, your thermostat will automatically adjust your HVAC system to use as little power as possible. It may switch to a higher temperature setting when you leave the house, bump down your AC in the evening, or do other little tricks to improve energy efficiency and environmental friendliness.


This is another mode that is mostly found on smart thermostats. It is only used in situations where the thermostat has a humidity monitoring system. Some systems may call this mode something like Humidity Control or AC Overcool. This mode works by running your air conditioner even if temperatures inside the house are comfortable. Running the AC will gradually remove excess moisture, helping to lower humidity in the house.

Dehumidification mode is useful if you live in a high humidity area but do not have a whole-house humidifier. By keeping home humidity below 60%, you can slow the growth of mold. More moderate humidity levels can also prevent wooden furniture from warping and keep electronics from getting damaged.

Have any other questions about how your thermostat works? Friar's Heating and Air is happy to assist you with all your HVAC needs in San Diego. In addition to helping you install and adjust thermostats, we can also repair, maintain, and install a variety of other heating and cooling equipment. Learn more about our services by giving us a call now.

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