Ecobee Smart SI Thermostat Review

General Information

If you are looking to buy one of the best Wi-Fi thermostats available, then read on our Ecobee Smart Si Thermostat review.

2 Heat – 2 Cool with Full Color NON-Touch Screen should definitely be one that you take a look at.  One important element that will influence your decision is, will the Wi-Fi enabled thermostat be compatible with your existing system? The good news with the Smart Si thermostat is that it is compatible with 95% of existing North American heating, ventilation, and air conditioning (HVAC) systems. The system was originally designed and developed with one purpose in mind – to save the money. Since the original system, saving money has remained a prime motivator but several highly useful features have been added along the way to increase ease of use and versatility.

  • The Smart Si monitors the local weather conditions and adjusts the heating or air conditioning accordingly.
  • Included is a feature called Free Cooling. This monitors the outside temperature and if it drops sufficiently, the Smart Si will switch from air conditioning and use the free outside cooler air.
  • The Smart Si comes with 3-year warranty, far longer than any of its direct competitors.
  • The Smart Si is compatible with dual fuel systems without the need to buy and additional module.
  • Included with the Smart Si is access to an IQ Energy report to allow you to monitor your monthly energy use and estimated savings.
  • The ecobee Smart Si thermostat is ZigBee compatible. ZigBee is the industry-wide standard for home automation, allowing the Smart Si to integrate with other home automation devices such as sensors. Although it may not affect you at the present, this is worth considering now as it will enable seamless integration should you need it in the future.
  • Although this mainly used for home HVAC systems it works equally well in commercial environments, such as offices.


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  • Compatible with 95% of existing North American HVAC installations
  • Adjusts the programming to suit outside weather conditions
  • Manual override for when you want a boost for up to 4 hours
  • Free Cooling, which will switch off the air conditioning and draw in outside air when the conditions allow
  • No monthly service charges
  • Free software upgrades
  • Online free IQ energy report
  • Can be programmed either from the thermostat or remotely from your PC or using the free ecobee mobile app
  • Compatible with PCs, Apple, Android or Blackberry smartphones
  • Emailed alerts to keep you up to date with what is happening currently with your system.
  • Adjustable brightness backlit display – always on
  • Suitable for dual fuel systems
  • A long, 3-year warranty manufacturer’s warranty


  • If you live in an area which experiences microclimates, the weather service that provides the information to the Smart Si may not be accurate enough
  • Due to its ability to connect with 95% of North American HVAC systems, there are several wiring variations that some users have found a little confusing and took a little time to distinguish which is appropriate for their system
  • It does rely on the ‘C’ wire to provide a power supply. If your existing system doesn’t have one then you either need to run a new supply to the thermostat or buy the optional power extender kit (PEK). Although needing a ‘C’ wire is a common situation with nearly all smart thermostats.


Ease of Use

Once you have installed the ecobee Smart Si thermostat and have the initial parameters set, it operates pretty much automatically. If an event happens that is outside of limits that you have input, the Smart Si will send you an email informing you. Any adjustment that you want to make can then be made remotely using your PC or the dedicated free ecobee mobile app.


The Smart Si thermostat is compatible with many existing thermostats to installation, in most cases, is straightforward. All you need to do is;

  1. Disconnect the wires from the old thermostat (they may need marking to ensure fitting to the correct terminals on the Smart Si).
  2. Connect the existing wires directly to the corresponding terminals of your Smart Si.
  3. For those systems that do not have an existing wire labeled ‘C’ (common) going to the old thermostat, a new wire needs to be run or the optional PEK (Power Extender Kit) is needed.
  4. Fit the included large back plate (which, in the majority of cases, will cover areas where an old thermostat has been removed avoiding leaving marks to your decoration).
  5. Follow the initial set-up instructions to input your location and the parameters that you want


There is an option to program your thermostat from either the thermostat itself using the menu and arrow keys or, which many users find easier and quicker, from a computer, smartphone or tablet using the dedicated ecobee mobile app.

Energy Saving

Ecobee claim that they can, on average, save homeowners 23% of the cost of their heating and cooling bills, although the actual amount you personally save will depend on a number of factors. You also have access to a home IQ Energy report. This allows you to see your monthly energy usage and estimated savings. It also shows areas where you could possibly make some adjustments to increase these savings even more.

Bottom Line

The Smart Si is quick and easy to install, easy to program (especially when using a PC or the mobile ecobee app), and can be controlled remotely from anywhere that you have internet access. The ecobee Smart Si does lack some of the features that some of its more expensive competitors have, but then it more that compensates by additional features that it does possess. Overall it does provide exceptional value for money and has a relatively short payback period. The ecobee Smart Si is one of the best Wi-Fi thermostats available and very well regarded among purchasers.