What is a smart thermostat?

Like conventional home thermostats a smart thermostat will manage your heating and cooling systems automatically, but what makes them ‘smart’ varies considerably. Many smart devices simply have a communication radio of some kind that allows them to be controlled remotely, usually via a smart phone app. They may also use this radio to enable integration with a smart assistant, like Amazon’s Alexa. Others employ more advanced sensors and features to make them truly smart, learning about how they are used in your home and automating those behaviors for you.

Smart Thermostats are cover a similar range of capabilities, from the simple voice controlled models, to the advanced learning models. In all cases you gain some degree of convenience in how you can manage the temperature of your home, and you’ll benefit from better energy efficiency by limiting the run time and temperature settings to suit what is going on at any given time of day.

Different smart thermostats offer differing features, connectivity options, and smart home support depending on how much you are prepared to pay. We have a range of buyer’s guides at the end of this article that will help you choose the right model for the features you want.

How do smart thermostats work?

Smart Thermostats connect to your heating or HVAC system in the same way as a conventional thermostat, by using thermostat wiring. This usually makes upgrading to a smart thermostat very easy as you can simply remove the existing unit and connect the wires right into the smart model, but there are some wiring variations that you need to consider up front.

Once powered up you can configure the setting you want via the thermostats smart phone app. You may be able to do this on the unit directly, but this depends on how much functionality is exposed by the hardware interface design. You will always have some degree of control on the face of the device, but many models will rely on the app to perform most advanced functions.

You can also configure your smart voice assistant to control your thermostat if it is supported. As with other smart devices, the voice assistants that it works with will vary, so be sure to choose a supported model before buying. This is an added convenience, but will usually only offer basic controls such as turning the system on and off, and setting the temperature.

How do smart thermostats save energy?

The more detailed settings options smart thermostats provide will usually allow for easily setting schedules for your temperature needs, be it through the week, or over the whole year. Better models will add to this the ability to determine if anyone is home, and even who that is, so it can adjust thing accordingly. Even this level of functionality can yield significant energy savings by not running the heating unnecessarily.

Smarter models will use on board intelligence software to monitor how the system is used, and when people come and go from the house. This data enables the thermostat to automatically make adjustments to temperature and run times to reduce energy usage.

Features like geofencing and smart sensors can be employed to determine when people are home, and even which rooms they spend the most time in during each part of the day to help optimize the system.

Saving energy is obviously good and will reduce your electricity bills. Not only that, but the efficiency gains are also significant enough that utility companies are frequently offering direct financial incentives for having one. See our detailed explainer on this for more information.


How do they save money?

Learn about energy saving features, rebates, and demand response incentives.


Who installs smart thermostats?

If you are replacing an existing low voltage thermostat, in most cases this can be done yourself. Most smart thermostat models are designed with easy to use wire terminals that you can simply insert the existing wiring into. These terminals will be labelled with letters like G, Y, R, or C. You only need to make sure the wires go into the same terminals as they came out of.

For high voltage, or line voltage, thermostats you can also do this yourself as the wiring is actually simpler, but you may be more comfortable using a professional for safety. Likewise if you are installing a thermostat for the first time, using a professional is advised to ensure that the wiring is run correctly to the HVAC control board.

What about the wiring?

For most HVAC system the wiring will be low voltage. This will consist of a number of thin colored wires connecting into various terminals in the back of the thermostat with different letters associated with each. Line voltage thermostats will have only a few thick red and black electrical wires, possibly connected with wire nuts.

With low voltage models, the main consideration is that your new thermostat has the same labelled terminals as the existing one to ensure you can use all of the features of your system. The other consideration is if you have a c-wire or not. This is often needed to power your thermostat, but there are options if you don’t have one. For more information on this see our c-wire guide below.


What is a thermostat c-wire?

Learn about c-wire installations, and options for when you don’t have one.


What is the best smart thermostat?

There are a variety of factors that will influence ‘the best’ smart thermostat for your particular situation, so we have compiled a series of buyer’s guides to help you choose based on your wiring requirements, smart home platform, preferred communication technology, or installation types.

Each of these guides is crafted to answer your questions and point out additional considerations that may weight into your choice, and we carefully select a range of options to suit different budgets and use cases in each category.


Smart Thermostats with no c-wire

No c-wire? No problem. These thermostats can work without one.


Smart Thermostats for Alexa

The best options if you specifically want to use it with Amazon’s Alexa.


Smart Thermostats for Z-Wave

The best options for thermostats that communicate via z-Wave.


Smart Thermostats for Australia

Australian HVAC systems are more complex, so we look at what you can use and when.


Thermostats that work with Ring

There are a few options now. See the best, and workarounds for others.


Thermostats that work with Homekit

There are more options than ever, but here are the best options for Apple users.