You’ve purchased a smart thermostat to replace the existing older type of thermostat in your HVAC system, but now it seems more difficult and tricky to install than what the salesperson at the shop has told you. Does this sound familiar? Don’t feel alone – there are many homeowners with the same problem!  

It is not so tricky to make the replacement if you follow the instructions step by step. In principle, you just have to disconnect the wires from the old thermostat, connect them in the correct order to the smart thermostat, and install it on the wall. Then you download the applicable app and set up your smart thermostat. 

In this article, we’ll give you the steps to follow to replace your existing thermostat with a smart thermostat. We’ll have a look at the physical installation and discuss aspects of the app and your Wi-Fi requirements. 

For readers who are still deciding whether they should or should not replace their existing thermostat with a smart thermostat, we will also discuss the differences between the older thermostats and the smart thermostat, and share some interesting details in this regard.

The installation process

A smart thermostat needs a common wire (C-wire) to operate.  (A C-wire runs from your low voltage heating system (24v) and carries continuous power to your thermostat.) If your HVAC system already works with a C-wire, the replacement of the older thermostat with a smart thermostat is relatively easy. 

Older houses with older types of thermostats generally don’t use a C-wire and the installation of the smart thermostat will need an extra step.

If you follow the steps as explained below, you will find it easy to replace your existing thermostat with a smart thermostat.

Step 1: Turn off your HVAC system

Before you start working on your thermostat ensure that your entire HVAC system is turned off. Turn it off at the breaker panel. Remember that your system might have multiple breakers. Turn off all the applicable breakers. 

When the power is cut, you can safely work on the thermostat and all the HVAC wiring without being afraid of any electrical shock. With the power cut, you also cannot accidentally cause shorting of electrical components when working on the system.

Some older thermostats that are battery-powered can sometimes appear to be on even when all the breakers have been turned off. To be a hundred percent sure the whole system is powered down it is recommended that you try to turn on the system at the thermostat and listen for any sign of an appliance start working. 

Step 2: Take off the faceplate

To get to the low-voltage wiring and backplate of the existing thermostat you’ll need to remove the faceplate of your old thermostat. Normally, it comes off easily. If it doesn’t, look for a hidden screw underneath and unscrew it. Depending on the brand and model there may be more than one screw to remove. If you don’t find screws and still can’t get the faceplate off, consult your electrician or HVAC expert. Never force it open. 

When you’ve removed the faceplate it is a good idea to take a photo of the wiring. You then have a record of which wires connect to which terminals. 

Some thermostats provide wire stickers to indicate the codes on the terminals. It is now the time to place the stickers on the wires. 

Step 3: Remove the backplate

The next step is to remove the thermostat wires from the backplate. Some thermostats have small screws holding the wires in place. Loosen them all to release the wires.  With some other thermostats, you need to press small tabs to release the wires. 

When all the wires are removed, use a screwdriver and remove the screws holding the backplate in the wall. Remove the old backplate.

Step 4: Add a C-wire if needed

If your existing HVAC system already has a C-wire, skip this step. 

If the system doesn’t have a C-wire, you have to add a wire to serve as the common wire. This will be the wire powering the thermostat. 

This is the one step where you call an electrician or HVAC expert if you don’t have enough knowledge regarding wiring and specifically C-wires. If the C-wire is installed and connected incorrectly, you risk damaging your whole system. 

Step 5: Put the new backplate in place

Use the new backplate as a template and mark the position where it has to come on the wall. Drill small holes for the backplate screws. Then pull the thermostat wires through the backplate and screw the backplate onto the wall. 

Step 6: Reconnect the wires

When you’ve securely attached the backplate to the wall, it is time to connect the thermostat wires to their corresponding terminals. This step is straightforward if you’ve labelled the wires with stickers before you’ve disconnected them from the old thermostat. 

If you haven’t labelled them, use the photo you’ve taken to match the wires and terminals.

Step 7: Snap the new smart thermostat’s faceplate in place

After you’ve completed all the wiring, snap the faceplate of the new smart thermostat onto the backplate. If it doesn’t fit easily, there are most probably some wires in the way.  Ensure that all the wires are tucked into the wall and then snap the faceplate onto the backplate. 

Step 8: Turn on your HVAC system

With everything in place, you can now turn the breaker for your HVAC system on. If the system is using multiple breakers you have to turn them all on. 

With power now coming to the thermostat, it will boot up. Remember, a smart thermostat needs time to boot up. 

Step 9: Connect the smart thermostat to Wi-Fi

Your new smart thermostat will now take you through a series of prompts to connect it to Wi-Fi and setting up the smartphone app. This process differs from brand to brand and model to model. Therefore follow the prompts closely. 

replacing old thermostat with smart

Wi-Fi and applicable app

A smart thermostat can only function fully if it pairs with an applicable app on a mobile device. The app is available from the same manufacturer as the thermostat and is normally a free download. 

So, before replacing your old thermostat ensure that the Wi-FI in your house is working. Unfortunately, Wi-Fi can sometimes be lost for short periods. If this happens your smart thermostat will still function as a “normal” thermostat. It will keep all settings as they were before the Wi-Fi connection has been broken. 

Different types of thermostats

There are three types of HVAC thermostats, namely the manual thermostat, the programmable thermostat, and the smart thermostat. 

Manual thermostats

The oldest and simplest type of thermostat is the manual thermostat. It is also called an analog thermostat. You set an analog thermostat to a specific temperature and the setting only changes when you manually adjust the temperature.  

Programmable thermostats

Programmable thermostats were first introduced more than 100 years ago. This type of thermostat allows you to schedule different temperatures for different times of the day. The idea of the programming is that if you can set a warmer or cooler temperature for the time of day when nobody is at home, you will save energy and money. Over years studies have found that the programmable thermostat is inherent a power-saving tool and can be very effective. But the problem is the human factor. 

Some homeowners don’t understand the principle or just don’t bother to set a schedule and change it when the season changes. Thus, while some homeowners are saving power and money by using programmable thermostats other homeowners just use them as manual thermostats. 

Smart thermostats

Smart thermostats are to a certain extent similar to programmable thermostats. However, the human “maintenance” factor is taken away. Just as the programmable thermostat, the smart thermostat has a scheduling feature allowing you to set different temperatures for different times of the day.

But after you’ve set the schedules the smart thermostat’s technology takes over and maintains the schedules to reduce the possibility of human error. The smart thermostat even has sensors that can determine whether or not the home is occupied and shut down the systems if not needed.

Some smart thermostats also offer geofencing to determine whether there are occupants in the house or not. A geofence is a perimeter created around the location of a smartphone or other smart device, based on GPS signals. 

As most people always have their smartphones with them the occupants’ phones will be outside the geofence when they are away from the house. A smart thermostat with a geofence feature will then sense that nobody is at home and shut down some of the systems. The systems will be put on again when somebody is returning to the house. 

Origin of the smart thermostat

It is interesting to know more about the origins of the smart thermostat. It all started in 2007 with a person with the name Stuart Lombard. He wanted to save energy and reduce his family’s carbon footprint. 

He realized that temperature control made up most of his home’s energy usage. To try to reduce their energy usage he bought a programmable thermostat, but quickly discovered that the programmable thermostat was difficult to use and unreliable. He started to design a smart thermostat that could save energy but was easy to use. He created a company to develop the idea further and the smart thermostat was born. 

Reasons to upgrade to a smart thermostat

There are different reasons why an upgrade to a smart thermostat is worthwhile, but the following aspects are according to many users the main reasons why they’ve replaced their old thermostats with smart thermostats.  

You can remotely change the temperature

It sometimes happens that you rush out of your home and when you arrives at your office you remember that you haven’t switched off your furnace or AC at home.  With a smart thermostat, it is no problem. You can put it off with your smartphone anytime from anywhere.  

And you can put it on again when you are on your way home after work and your house will have the right temperature when you arrive there.

You save money on your electricity bill and maintenance

The most important feature of smart thermostats is that they save you money. Your smart thermostat can be set to activate the HVAC appliances only during certain hours and thus save electricity. Some thermostats can be set to automatically switch off your HVAC system when nobody is home. Again you save money. 

You also save on maintenance costs as the appliances are not running all the time. 

You have control over the temperature in your home

Your smart thermostat gives you greater flexibility regarding the temperature levels in your home. With zoning, you can have different temperatures in different rooms. You don’t have to have the same temperature throughout your house.

Smart thermostats improve your indoor air quality

Your smart thermostat warns you when your filters need to be changed. It will even let you know when you have to make your next maintenance call.  The clean filters help improve the air quality in your home.


We hope that this article has assisted you to replace your existing thermostat with a smart thermostat. As indicated, it is not so tricky that it cannot be a DIY job. 

You just have to follow the steps and only have to call an electrician or HVAC expert if you encounter problems with aspects like installing a C-wire. The apps of all the different brands are normally easy and simple to use. 

For the readers who are still deciding whether they want to upgrade or not, we’ve given some things to keep in mind in their deciding process. We think you’ll now be able to make a more informed decision.

The bottom line is that smart thermostats are relatively easy to install and apart from the comfort it offers you once they are installed, you start saving electricity and money immediately.


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