Programmable and smart thermostats are the latest technology in heating, ventilation, and air conditioning (HVAC) control. Programmable thermostats can be set to change temperature settings based on the day or the week or the time of day. Smart thermostats make changes to temperature settings automatically based on whether you are home or not and based on how you make adjustments to the system during its learning period. Either thermostat can save you money and help you conserve energy, but not every HVAC system can handle a smart/programmable thermostat. Here’s what you need to know when considering a thermostat upgrade.
Forced-air systems can usually handle both smart and programmable thermostats. In fact, these thermostats are designed primarily to be used with forced-air systems. The big exception to this general rule is heat pumps. If you have heat pump, then a programmable thermostat can actually ruin efficiency when the pump is in its heating mode. You are fine to use a programmable/smart thermostat while the heat pump is in cooling mode (acting like an air conditioner), just not when it is in heating mode. There are a few programmable thermostats that are now designed to tell the difference between heating and cooling modes and will work fine in either setting. Some smart thermostats may also work fine in these situations, but you’ll have to check with the manufacturer first. If your forced air system relies on electricity to generate heat, read the next section on electric resistance.
Electric resistance systems (electric baseboard, electric forced-air, and radiant electric heat) usually work with much higher voltages (120-240 volts) than forced-air systems (24 volts). Standard programmable and smart thermostats cannot operate at high voltages. There are a limited number of thermostats that are manufactured specifically for electric resistance systems. Check with the manufacturer or an HVAC technician to see what your electric resistance system requires.
With the exception of electric radiant heat, radiant systems have very slow response times. They can take several hours to reach a temperature setting and so don’t do well with constant changes. In truth, radiant systems are about 30% more efficient than forced-air systems to begin with, so you really don’t need to worry about setbacks and “away” settings anyway. A simple and inexpensive manual thermostat is the best option for radiant systems, though there are few thermostats that will track usage patterns to help you figure out if and when you could change temperature to save money without affecting comfort.
Generally speaking, if you have a forced-air system that doesn’t rely on electric resistance heat then there is a programmable or smart thermostat out there that will suit your needs. If you have an electric resistance system of any kind, check with the manufacturer or an HVAC technician to determine if it requires a high-voltage thermostat or not. If you have a radiant system, you already have the most efficient heating system available, so stick with your inexpensive manual thermostat and be happy.