Smart thermostats provide all the basic scheduling features of programmable thermostats, and, depending on the model, they can provide the ability to:
If you’re an avid DIYer with some experience replacing or installing new electrical receptacles and switches, you should have no problem installing a smart thermostat. Otherwise, it’s best to hire an electrician to do the work for you. Installation is a 15- to 30-minute job. Once installed, most smart thermostats will automatically connect to your Wi-Fi router. You’ll also need to install the thermostat’s app on your mobile device to configure and manage its various features.
Most home HVAC systems (whether comprised of a single furnace or some combination of furnace, air conditioner, heat pump) are connected to a thermostat that draws 24V of power (referred to as a low-voltage thermostat) from a transformer generally located on the furnace. Homes with a baseboard and/or radiant heating system are usually connected to a thermostat that draws 120V of power (referred to as a line voltage thermostat). When purchasing a smart thermostat, you need to know how your existing thermostat is powered, as most smart thermostats are only compatible with 24V systems.
On a 24V system, the thermostat sends its signals to the HVAC system via a set of three or more bundled wires. Usually one of those wires is the common wire (C-wire), which smart thermostats use. Occasionally there is no C-wire (particularly with older HVAC systems), in which case you (or an electrician) will need to add a common wire. This involves replacing the wire bundle that runs from the thermostat to your HVAC, a fairly straightforward procedure. For those systems without a C-wire, the Ecobee 3 provides a Power Extender Kit that connects to your HVAC system, enabling you to use the furnace fan wire in place of the C-wire. The Nest doesn’t require a C-wire, but will use it if present. One of the few companies to offer line voltage smart thermostats is Sinopé Technologies.
In some homes, the HVAC system uses a series of valves and dampers to control the temperature independently in different areas of the house. This is referred to as a zoned system. If you have a zoned system there will be a separate thermostat controlling each zone. In a situation like this, you won’t be able to replace all the thermostats with a single smart thermostat – you’ll need to purchase separate smart thermostats for each zone. Even though most smart thermostats are compatible with multi-zone systems, none can control more than one zone.
Some homes have a heat pump that takes care of most of the heating and cooling, and a gas or electric furnace that kicks in during the colder months, when the heat pump operates less efficiently. Usually both are connected to the same thermostat. This is a dual fuel, or hybrid system, and only The Ecobee, Nest and Sensi Touch are compatible with them.
Algorithms are essentially mathematical instructions embedded in the microcontroller inside most smart thermostats, used to control various operating features – such as instructing the thermostat to turn the air conditioner on if the indoor humidity increases to a specific level, or to turn the heating down when you leave the house. The Nest is most closely associated with the concept of self-learning algorithms designed to learn about your temperature preferences on their own. With most smart thermostats you program your daily temperature preferences – waking, during the day, coming home, going to bed, weekends, and the like. With the Nest, once installed you still have to adjust the thermostat to your preferred comfort levels a few times a day during the first few days, but it quickly ‘learns’ those preferences and automatically adjusts the temperature as required.
Some thermostats have built-in sensors that illuminate the display as you approach the thermostat, measure room temperature and humidity levels, or detect when you leave a room. Only the EcoBee3 uses wireless remote sensors that detect where you are in the home, and will adjust the temperature accordingly. It also enables you to add up to 32 different sensors throughout your home.
It’s convenient to be able to control the majority of a thermostat’s features via a touchscreen as well as through the app. Screens vary in size and clarity, and some light up as you approach them. Some default to a nightlight mode at nighttime.
Geofencing is a feature that uses GPS to enable a thermostat to know when you leave your home, and when you’re within a specified distance from home, so that it can better regulate temperature. This means that you don’t have to program the thermostat to turn on or off at times you typically enter or leave your home, or activate an ‘away’ mode – as long as your mobile device is connected to the smart thermostat. However, if there are multiple residents, then each will need to be connected to the thermostat’s app for geofencing to work properly.
If you use a smart-home hub or smart speaker, then you’ll want to select a compatible smart thermostat. This facilitates integrating with any other smart devices in your home. Only the Sinopé lacks any hub connectivity; all others are compatible with at least one hub.
This Canadian product has received a lot of positive feedback from consumers. It’s compatible with just about any heating and cooling system, whether the system uses a C-wire or not. The EcoBee relies on sensors to control temperature. There’s a built-in sensor, and it comes with one remote wireless sensor that you can place anywhere in the home (you can add up to 32 additional sensors). It also uses geofencing to detect when you leave or return to the home. Initially you’ll need to set up a temperature schedule (or use the default schedule provided by EcoBee). The EcoBee uses its sensors and geofencing to manage this schedule when you move about the home and when you’re away from home. It’s one of the few smart thermostats that is ENERGY STAR certified. There is a Lite version of the EcoBee3 that doesn’t provide support for accessories such as HRVs, ventilators, humidifiers, and dehumidifiers. The upcoming EcoBee4 will feature built-in Amazon Alexa voice control.
Honeywell has nine different Wi-Fi enabled smart thermostats, three of which are part of the Lyric line. The Lyric T5 is the newest version. It features geofencing and the usual seven-day scheduling, along with smart alerts – for example, telling you when to change the furnace filter. You can use the Lyric app or the touchscreen to control the features. It doesn’t work with dual-fuel systems and lacks a built-in motion sensor. However, it’s one of the least expensive models to purchase.
Nest is the granddaddy of smart Wi-Fi thermostats and is generally viewed as the benchmark against which other models are compared. It learns your temperature preferences and your schedule of coming and going, how quickly your home heats up and cools down, and pairs that information with local weather conditions to maintain an optimal temperature throughout your home. Like the EcoBee, it uses geofencing, has scads of features, and works with all the major smart devices and systems except Apple’s HomeKit and Samsung’s SmartThings.
The Sensi works with dual-fuel systems and uses geofencing. It has one of the largest high-definition colour display touchscreens, which might be of special interest to anyone with visual issues. It also meets the new Energy Aware standards requiring plus or minus 1 degree of accuracy in temperature control.
This Canadian company has thermostats for both low- and high-voltage systems, as well as for radiant floor heating systems. Their products run off the Sinopé ‘neviweb’ platform, and you need to purchase their GT125 Web Interface for Wi-Fi compatibility. This model offers a basic set of functions, including a clock and temperature display and a 7-day schedule with up to six different temperature periods per day. However, it lacks a built-in sensor and doesn’t use geofencing.
Carl Duguay - [email protected]
Carl is a Victoria-based furniture maker and the web editor at Canadian Woodworking & Home Improvement.