Smart or programmable thermostat: how to choose

What is the difference between smart and programmable thermostats?

A programmable thermostat stores a weekly schedule with a few set points, for example a lower night temperature and a lower daytime one when nobody is home. It runs that schedule with no internet connection. Models differ in how many schedule periods they allow, and some let you separate weekdays and weekends.

A smart thermostat does the same and adds connectivity. You can change the temperature from a phone app, link it to a voice assistant, see run-time reports, and get alerts. Some learn your habits, some use sensors or your phone's location to detect when the house is empty, and some can coordinate with other rooms through remote sensors. Features, interfaces and privacy settings vary by brand, so read what data a device collects. The potential savings of the smart route are covered in smart thermostat savings in Canada.

Which one suits your household?

Think about how your days actually run. If you have a steady weekday routine, work out of the house on set days and live by the clock, a programmable thermostat captures most of the benefit. Once the schedule is set, it just works, and it does not depend on an app, an account or updates.

A smart thermostat earns its extra cost where life is irregular: shift work, travel, a holiday home, children coming and going, or a wish to adjust the house from elsewhere. It also helps if you tend to forget to turn the heat down. Manual adjustment is the baseline for comparison. If you already turn the heat down by hand at night and when you leave, a programmable model is close to enough. If you never touch it, either type is an improvement, as long as you use it. Our guide to lowering the winter heating bill covers other steps that cost little.

Will it work with your heating system?

Compatibility is where many installations go wrong, so check before you buy. The main points:

• Voltage. Furnaces, boilers and central air usually use low-voltage (24 V) control. Electric baseboard heaters and some other electric heaters use line-voltage thermostats on the mains, and a low-voltage model will not work. Line-voltage smart models exist, but the choice is smaller.
• Common wire. Many smart thermostats need a common wire, often called a C-wire, to power their screen and Wi-Fi. If your wall has no spare wire, an adapter or a different model may be needed.
• Heat pumps. A heat pump needs a thermostat that handles the reversing valve and, if there is one, a backup heat stage. A set-back schedule can also trigger expensive backup heat if it is set badly; see heat pump thermostat settings.
• Multi-stage and variable systems. Two-stage furnaces and modulating equipment need a thermostat that supports their stages.
• Radiant floors and zoning. Slow systems and zoned systems may need specific controls. A zone panel usually has its own thermostats, as in the zoning guide.

The thermostat's manufacturer usually publishes a compatibility checker, and an HVAC technician can confirm. Turn off power at the furnace or breaker before touching any wiring, and take a photo of the old wiring first.

What should you compare before buying?

Set the features you will really use against the price. Look at the number of schedule periods, whether it works well without Wi-Fi, how it handles a power cut, the display and buttons, sensor options and how easy it is to override a schedule. For smart models, check which app platforms are supported, what happens if the company stops supporting the app, and how data is stored. Ask whether your utility or province runs a rebate on thermostats, since some do, and verify the terms on the official page before you buy.

Installation is simple for many households, and a contractor can fit one during other work, for example a furnace installation. Whichever type you choose, set sensible set-back temperatures, test the schedule for a week, and adjust it to your comfort.

Quick answers