If you want to know how to install a smart thermostat, this is the best guide for you with features you should look for in a thermostat. This article is step two in our How to Build a Smart Home series, which takes a beginner through the process of selecting the right components for their home automation needs. Read this article if you haven’t installed a smart thermostat in your home.

A thermostat is usually one of the first intelligent devices people add to their homes. The main reason for this is the convenience and comfort of arriving home to a house set at the perfect temperature. Even better, you save money on utilities since the thermostat automatically adjusts the temperature when you are away. Some units even monitor your adjustments and automatically adjust the schedule to match your preferences.

Before you click the buy button, there are a number of things you need to pay attention to when choosing the best smart thermostat to Install Smart Thermostat in your home.

Line Voltage Smart Thermostat vs Low Voltage Smart Thermostat

Most heating and cooling systems use low-voltage smart thermostats, which draw 24 volts of electricity. These thermostats run most modern systems like furnaces, heat pumps, and many boilers. The wires are usually 18-gauge and have 2, 4, 5, or 8 conductors (each of which has a different color jacket). 18-gauge wire is fairly thin with a diameter of only 0.04″. If your thermostat has thin wires connecting to a terminal block with coded terminals, you have a low-voltage thermostat. In this case, you have a few great options for your smart thermostat. The next step is to make sure you have a common wire.

However, electric baseboard heaters and convectors require a line voltage smart thermostat that can handle 120 volts of electricity. Some radiant floor systems also use line voltage controls. You can recognize line voltage thermostats because the wires are much thicker at either 14-gauge (0.06″ diameter) or 12-gauge (0.08″ diameter). These wires do not connect to a terminal. Instead, they are tied directly to the line voltage wires serving the electric heater. If you open your thermostat and see wires connected with wire nuts, you have a line voltage smart thermostat. You can also look for the voltage label on your old thermostat. If you see 110V or 120V, you have a line voltage system.

line voltage smart thermostat

Unfortunately, there are fewer options for smart line voltage thermostats. We recommend checking out the Mysa Smart Thermostat or the Stelpro Maestro Thermostat.

Make sure you have a common wire for smart thermostat installation

Wi-Fi thermostats require a constant power flow to keep the Wi-Fi connection and the colorful display operating. The common wire gives the thermostat a continuous supply of 24 volts of power. However, some simple or older systems may not have a common wire. We have a very detailed article about common thermostat wires, which helps you determine if you have a common wire and what to do if you don’t have one. There are many Wi-Fi thermostats without C-wire available in the market, which you can buy to install a smart thermostat at home.

thermostat wiring diagram
Identifying a Common Wire

If your current thermostat has a wire connected to the C terminal (usually black or blue), you have a common wire and can use any low-voltage Wi-Fi thermostat. If you don’t see a wire connected to the C terminal, check inside the wall to ensure the wire isn’t simply disconnected. You can also check the circuit board at your HVAC unit to see if a wire is connected to the C terminal.

HVAC system compatibility check to install a smart thermostat

We just talked about checking your wiring, but before you make a selection, you should do a final check to ensure your HVAC system can work with your selected thermostat. First, check out the manufacturer’s website and use their compatibility tool. All of the big manufacturers have them. Checking compatibility is especially important if you have an HVAC system other than a furnace, boiler, or heat pump. However, we recommend you check, no matter what system you have. Each of our reviews has a link to the manufacturer’s compatibility checker.

Once you have confirmed your wiring situation, it is time to think about the features you want for smart thermostat installation.

Important Features of the Best Smart Thermostat

Low-voltage smart thermostats usually have similar features, so you should be good with any choice. Line voltage thermostats have fewer features, but they are catching up quickly. Let’s review some key features of the best smart thermostat.

Thermostats for Multiple Zones

Small apartments can function with a single thermostat. However, multi-story or very large homes tend to have multiple heating and cooling zones that operate independently. That way, you can have the heat set to one temperature upstairs and a different temperature downstairs. If you have multiple zones, you will need to purchase a smart T-stat for each zone.

Multiple zones work because the thermostat wires all return to a central zone management system. That controller reads each thermostat signal and then tells the HVAC equipment what zones need to be activated so that you can adjust the dampers or valves. Unfortunately, there are occasional compatibility issues with older zone controllers. We recommend a quick internet search for the model number of your controller and the thermostat you are considering. You will probably be OK, but you may have to purchase a new zone controller for a couple of hundred dollars.

thermostats for multiple zones HVAC control

Multi Zone HVAC control

Some manufacturers are working on a true multi-zone system with a central control panel and a series of zone sensors. However, these aren’t widely available in North America at this time. So instead, you can buy smart thermostats for multiple zones online.

Extra Temperature Sensors

You may find that you have hot or cold spots in your home. Uneven temperatures can happen when the thermostat is located in a central hallway, but an occupied room gets more/less sun or has poor insulation. The thermostat senses that the temperature is fine, but you are uncomfortable.

The solution is to install remote sensors, which send temperature information back to the thermostat. You can then program the system with priority information for different times of the day. For instance, you might tell the thermostat that its internal thermometer should control the system during the day. However, you can tell the system to pay attention to the remote sensor in your bedroom at night.

Some remote temperature sensors, Ecobee, for instance, also have a built-in motion sensor that will prevent the system from going into Auto-Away mode. If your thermostat is located in an area of your house that people don’t walk past, it might think you are away and adjust the temperature accordingly. Suddenly you feel uncomfortable, realize the system thought you left the house, and now you have to wait for the temperature to return to the right setting. Remote motion sensors can help resolve this.

Remote sensors have a low-power radio that talks to the thermostat and a replaceable battery that lasts for a year or more.

Learning Thermostats

Nest learning thermostat has an interesting feature that allows you to skip manual programming. All you do is turn the temperature up and down for about a week, and then the Nest programs itself, based on your preferences. It isn’t a perfect feature, so most people adjust the settings. However, this can save you a bit of time and frustration when first starting out.

We don’t think this is a critical feature since most people already know what temperatures they prefer at different times of the day. In addition, the apps provided for the thermostats make it very easy to adjust the programming. However, if you want the device to program itself, go with a learning thermostat.

Energy Saving Suggestions for Smart Thermostats

Many people like to receive regular reports that help them understand how much money they are saving. These reports also help people strive to save more money on their utility bills — it is like turning your thermal comfort into a game. We recommend tracking your energy usage for all thermostats and providing a report that helps you achieve more savings.

As software improves, we expect more features that help people save energy, which saves you money.

Automatic home/away adjustments

Most of the smart thermostats on the market have motion detectors so they can determine that you aren’t home and automatically adjust the temperature. Motion detectors are great for when you forget to adjust the temperature before going on vacation or when you are home in the middle of the work day. Unfortunately, it can also be a bit annoying if the thermostat thinks you are home or away when you aren’t. However, a few dollars of energy savings might be worth having this feature.

If your thermostat is located in an area of your home that doesn’t see much foot traffic, you may want to turn this feature off. The other option is to select a manufacturer that sells remote sensors that can also detect motion, like Ecobee.


You can set your smart home apps to monitor your location (via your cell phone) and perform certain actions when you are in specific places. For instance, you can program your thermostat to adjust the temperature when you leave work after 4 PM. That way, the temperature starts to adjust before you arrive home. Geo-fencing is the name of the feature that runs a program when you physically enter or leave a digitally “fenced area.”

Geo-fencing is important for some smart home devices like lighting, where you want to turn the lights on when you pull into the driveway. However, we don’t think it is a critical feature when choosing a smart thermostat. Geo-fencing can be quite confusing, and sometimes, it can lead to more energy use. Based on our previous example, let’s say you program your thermostat to adjust the temperature when you leave work after 4 PM. However, tonight you are meeting some friends for dinner from 5 PM to 8 PM. Now, your HVAC system will be running unnecessarily for 3 hours.

Compatible hubs to install smart thermostat

Now that you’ve identified the features you want in a smart thermostat, it is time to consider your smart hub. Of course, you can use a thermostat app, so you don’t necessarily need a hub. However, if you want to control all of your different smart home components from a single app, then you need to make sure your thermostat works with your chosen hub. Our thermostat review pages give you info on what hubs and systems each thermostat work with.


ENERGY STAR is a US EPA program that helps people save energy by developing criteria and certifying products. All smart thermostats will help you save energy, so this isn’t a major criterion. However, the ENERGY STAR rating means that the thermostat meets strict energy-saving guidelines. You can read more about the thermostat guidelines on the Energy Star website. Here are the requirements that manufacturers need to meet to be certified:

  • Work as a basic thermostat without connectivity to the service provider.
  • Give residents some form of feedback about the energy consequences of their settings.
  • Provide information about HVAC energy use, such as monthly run time.
  • They should provide the ability to set a schedule.
  • Provide the ability to work with utility programs to prevent brownouts and blackouts while preserving consumers’ ability to override those grid requests.


Energy rebates

There are a lot of state programs that offer a rebate for purchasing a programmable thermostat. Check your electric or gas utility’s website for rebate information. In addition, each thermostat manufacturer has a page on their website dedicated to rebates. Make sure you take advantage of these programs when you purchase a smart thermostat because you can save around $100 (or more) for a programmable Wi-Fi thermostat. So finally, after checking all these features in a thermostat, you can also calculate the smart thermostat installation cost.