Controlling Your Heating and Air Conditioning HANDS ON with Amazon Alexa

You guessed right, it is home automation week here at VoiceDesigned!  

A great project you might be interested in seeing to completion is that of upgrading your thermostat so that you can control your heating, ventilation and air conditioning systems (HVAC) from anywhere!  This article looks at the Sensi Smart thermostat and covers installation, setup and Alexa integration.  There is no support for Google Home yet.   There are a number of different thermostats available from Amazon which support WiFi, and you are always wise to find the one which is right for your situation.


The Sensi Smart Thermostat has built in Wifi and supports controlling both heating and air conditioning systems.  There is a (free) mobile App for iOS and Android (but no tablet app) that you need to download and start.   You can view temperature and turn the heat/air conditioning up and down remotely, as well as have the ability to add a schedule for automatic device operation.

By far, the trickiest part is installing the device.  This is what took the majority of the time, and is not so much a fault of the device but the great number of furnaces it must interface with. There is some setup involved around the iPhone App, and finally there is a whole separate step to setup Alexa to integrate with the thermostat.


A new thermostat is usually a device which you are replacing your current one.  There are many different manufacturers (and types) of furnaces and air conditioning units.  It turns out, there is not really any standard for how those get connected.  This also relates to how old the furnace and air conditioner are at your house.  The only tool you'll need for this step is a screwdriver.

Other than taking down your old thermostat, putting on a new wall plate and mounting the new thermostat, the tricky part is to get the wiring correct. This pictue shows the new face plate at the top, with the one I previously had.

Luckily, the Sensi App has step by step instructions that really does walk you through the process.   It reminds you to take a picture of your current wiring, just in case.  It then proceeds to help you connect the wires, as labeled on your old thermostat to those on your new thermostat.

In my case, I only have a heater, and it is an older house, with the furnace serial number indicating it was manufactured in 1978!  Yes, that old.  Although there were labels on my old thermostat, the common wire, which is required on the Sensi (to provide power for WiFi) was not wired through my system.   I had to go back to the furnace, determine what wire I needed (and none of them were labeled) and then take one of the unused wires already going to the thermostat and re-purpose it for this new common wire.  

There are only two screws holding the thermostat plate to the wall, and they are easy to put in.  I like the added touch of the built-in level at the top, which makes sure I put it on straight.  The following is a picture showing the wires set into the faceplate for the sensi.  You'll need to move all wires into the center area, as the thermostat itself will not fit with wires sprawling around.  

I do not have any background in HVAC, and I did need to call the Sensi help desk to get it all figured out.  However, I am happy to say that the two technicians I spoke with were helpful in pointing me to solving my problem, and I was quickly able to get the correct wiring in place.

Setting Up the Sensi Thermostat

Having gone through the step-by-step instructions, you will get to this point, where you need to setup the device to your Wifi, register it, and you give it a name.

You'll need to give it a name, which you can change later.  You'll want to give it an appropriate name, as that is what you will use for voice commands.

The other area you can setup now, or hold off until later is setting up a schedule.  The App has a nice user interface for setting this up.  You can have a regular schedule with is different on weekends as well.  The overall idea is that you can setup at what time the thermostat gets set to a certain temperatue.  In that way, you can have it automatically regulate through the entire day.  You'll need to turn schedule on from the Thermostat itself (rightmost button on the bottom), before you can set one in the App.

This part of setup is trivial with comparison to having to get out your screwdriver to mount the thermostat on the wall.  When it is complete, you will be able to use the App to remotely control the thermostat.   All the controls on the device will also work at this point.

Integrating with Alexa

But, there is one more step required to get 'Full Home Automation Nirvana', and that is integrating with Alexa.  This step is actually pretty easy as well.  It is just that the Sensi App's step-by-step instructions end without mention of Alexa integration.  You'll need to start-up the Alexa Companion App and choose the hamburger menu and select Smart Home.


Next, under the section for Your Smart Home Skills, choose the Get More Smart Home Skills option.

This takes you to a list of home automation skills.  Scroll down in the list, or type the word Sensi for it to show up at the top of the list and click Enable.

The Alexa Companion App should prompt you to enter your Sensi login and password.  This is part of account linking and required to complete the integration.  The last step is to choose Discover devices from the menu.  This will scan all your smart skills and add the new skills for the Sensi thermostat.

Voice Commands

Assuming the previous steps completed succesfully, tou should be set!  Not only can you use your mobile phone to control your thermostat, you can also use voice.  Try commands like:

  • "Alexa, set thermostat to 79 degrees"
  • "Alexa, raise thermostat by 2 degrees"
  • "Alexa, lower thermostat by 3 degrees"

I called mine (simply enough) thermostat, but you would use whatever name you gave yours.  A larger or multi-level house could easily have multiple thermostats as well, so giving each a unique name lets you control them independently.

Unfortunately, there are no voice commands to ask for the current (indoor) temperature.  Asking Alexa just gets you the weather report.  Above, I have stated termperature in degrees ferenheit.  If you live in the 95% of the world that use centigrade, that is no problem as well, although make sure to set centigrade as the units in both your Sensi App along with the Alexa Companion App.  


I hope this gave some insight into the benefit of voice control for a thermostat which is tied into home automation.  The Sensi is a great thermostat that works perfectly for myself and my familly.  You can also do custom things like turn off the controls on the device from a remote location.  This gives you even more control, and takes away the worry of somebody locally overriding your settings.  Finally, don't forget about the usual features which let you set a schedule for your heating and air conditioning units.




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