Skip to Content

Can You Have Two Smart Thermostats In One House?

Smart thermostats are gaining more and more traction. These devices track and learn your behavior, saving you money down the line. However, some homes may benefit from having two or more smart thermostats.

It is possible to install two smart thermostats in one house. Having two thermostats wired to the same HVAC unit allows you to evenly condition your home. With the use of zones, control, and dampers, you can regulate your home from top to bottom. However, installing two can be complicated.

Multiple thermostats allow for more accuracy and efficiency. Having two of these devices seems like a no-brainer, right? Before you purchase a second thermostat, there are some caveats and additional considerations to take into account. Here’s everything you need to know about installing two smart thermostats in one home.

What are Smart Thermostats?

Thermostat indoor smart home in house system for temperature

To understand how smart thermostats save you money, you first need to understand what they are and how they work. There are three main types of thermostats: non-programmable, programmable, and smart thermostats.

Non-Programmable Thermostats: Non-programmable thermostats are traditional and dated. Most of us are familiar with this type of thermostat. These thermostats allow you to manually adjust temperature levels within your home.

Programmable Thermostats: One step above traditional thermostats are programmable options. These thermostats allow you to heat and or cool your home at certain schedules and intervals. These thermostats are programmed manually and do not have mobile connectivity. Many homeowners have found programmable thermostats to be clunky and frustrating to use.

Smart Thermostats: Finally, we have smart thermostats. Smart thermostats connect to the internet via WiFi. These devices allow you to control your home’s temperature via phone apps or from the internet. Some smart thermostats have machine learning algorithms, allowing them to find and set the most efficient schedules. Additionally, smart thermostats can connect to devices such as Amazon Alexa, Google Home, and Apple HomeKit.

How Many Thermostats Do You Need?

You may be wondering how many thermostats you need to control the temperatures of your home. I mean, how can one tiny device heat and cool your entire house?

In some cases, you’ll need two thermostats to heat your entire home. However, there are some caveats and factors to consider before purchasing.

What Should I Consider Before Purchasing a Second Thermostat?

Some situations call for multiple thermostats. How many thermostats you need comes down to your heating zones, the type of building you’re in, and how many stories there are.

Consider Your Home Type

The first factor you should consider is what type of home and building you’re residing in. Different homes will require varying levels of energy to regulate the temperatures.

For example, a two-story apartment will have different requirements than a single-story townhouse.

Consider How Many Stories You Have

The number of stories your home or building has will determine how many thermostats you need. Single-story homes typically get by with just one smart thermostat that can heat and cool the home completely.

However, multiple-story buildings, homes, and apartments may need more than one thermostat.

Consider The Zones

Zoning is the process of dividing a home or building into different sections, rooms, and zones. If your home has more zones than a single, smart thermostat can support, you’ll need another one.

For example, you may have a thermostat for the upstairs and downstairs portion of your home.

However, not all smart thermostats are created equal. Some devices can only control one zone, while others can control multiple. The Ecobee Smart Thermostat (on Amazon) can set and regulate up to 16 zones, all controlled from an app on your phone.

Can You Have 2 Thermostats on One HVAC Unit?

Large homes are notoriously difficult to heat and cool. Fortunately, it’s possible to have two smart thermostats connected to one HVAC unit.

Having two thermostats wired to the same unit allows you to evenly condition your home. With the use of zones, control, and dampers, you can regulate your home from top to bottom.

What Do You Need to Install Two Thermostats on One HVAC Unit?

You’ll need a few tools and materials before you begin installing an additional thermostat. You may need:

  • Multi-stranded 18-gauge thermostat wire
  • Two thermostats
  • Pointed pliers
  • Screwdrivers
  • Zone dampers
  • Zone control box

You can find these tools online or at your local hardware store. Be sure to read all of your manufacturers instructions and guidelines before beginning.

How to Install Zone Dampers

You need to install zone dampers before you can begin installing your smart thermostats. Zone dampers use your existing HVAC system and create multiple zones, allowing you to control certain areas of your house more accurately.

Step 1

To begin, start by drawing a simple diagram of your HVAC duct system. Determine which rooms are fed by each of the supply air ducts within your home.

Mark those ducts with a marker and find where your duct separates into the two zones of your home. Be sure to accurately measure the ducts and purchase the correct dampers.

Step 2

From there, cut a hole in your ductwork big enough to fit your zone damper. Different zone dampers have different instructions, so be sure to read the guidelines.

From there, secure your zone damper with screws and seal with a silicone caulking agent. Rinse and repeat this step until you’ve installed all the dampers.

Step 3

Afterward, strip the ends of your 18-gauge thermostat wire and attach it to the damper’s wire holes. Typically, zone dampers will have two or three wires. Be sure to run the attached wire to your zone control box.

Step 4

For step four, strip the ends of the wires from your zone damper. Attach the wires to your zone control box in the marked areas.

These areas should be marked “Damper 1” and “Damper 2.” Each damper will require two screws. After everything is attached, tighten the wires with a screwdriver.

Step 5

Place your zone control box near the furnace. This location can either be on the ductwork itself or on a close wall.

Afterward, run your 18-gauge 4-conductor wire from the control interface on your furnace to the proper terminals marked on the zone control box.

Step 6

Finally, strip the ends of the 18-gauge 4-conductor wire and attach them to your furnace’s control board. The wires should be attached accordingly:

  • White to W
  • Red to R
  • Green to G
  • Yellow to Y

Be sure to attach the other end of the wire from the zone control box to the proper color-coded terminals.

How to Install Two Thermostats on One HVAC Unit

Smart home automation woman using phone app regulating indoor temperature regulation smart house screen system

After you’ve successfully installed your zone dampers, you can begin installing your new smart thermostats.

Step 1

To begin, install your thermostats in the areas of your home being fed by the zoned ducts. Follow the instructions and guidelines included with your thermostat. From there, run a wire from each device to the zone control box.

Step 2

Afterward, connect the wire from your thermostat being fed by Damper 1 to the proper terminal. The terminal should be marked Thermostat 1. Rinse and repeat this step for the second device, but attach the wires to the terminals marked Themerstat 2. The wires should be color-coded accordingly:

  • White to W
  • Red to R
  • Green to G
  • Yellow to Y

Step 3

Finally, you can now test each thermostat to ensure your home is properly heated, cooled, and regulated.

Best Thermostats for Multiple Zones

There are a wide array of options. Suppose you’re considering using multiple thermostats. Not to mention, not all smart thermostats are created equal.

Some have more compatibility options and features, while others can save you more over the long run. So, what thermostats should you consider for multiple zones?

The Nest Learning Thermostat

The Nest Learning Thermostat is one of the most popular smart thermostats on the market. According to their studies, this thermostat saved 10% to 12% on heating and 15% on cooling.

Based on these savings on typical energy costs, you may be able to save up to $150 a year. However, this device doesn’t come with remote sensors and must be purchased separately.

Ecobee4 Smart Thermostat

Another popular device is the Ecobee4 Smart Thermostat (on Amazon). This device is fully programmable both in-person and through its mobile app. Ecobee’s Smart Thermostat can control up to 16 zones right out of the box, making it incredibly efficient.

Ecobee also sells additional sensors (on Amazon) at affordable prices.

Ecobee claims their smart thermostat can save homeowners upwards of 26% annually. Although the average utility cost varies, Ecobee’s Smart Thermostat could be saving homeowners $100 to $300 a year.

Ecobee3 Lite Smart Thermostat

The Lite Smart Thermostat by Ecobee (on Amazon) is another fantastic choice. Although it lacks features from their newer models, the Ecobee3 makes up for it with its competitive price point. At under $170, this thermostat is the most affordable option on our list.

However, this device doesn’t come with a remote sensor, lacks built-in features, and maybe less compatible than other options. Be sure to check if the Ecobee3 Lite Smart Thermostat is compatible with your home before purchasing.