Regular thermostats let you adjust the temperature in your home—it’s just a control panel for your heating and air conditioning system. Programmable thermostats let you set the temperature and have the thermostat change it based on the time of day.
What makes most smart thermostats so “smart” is that they learn from your behaviors, allow you to control the climate in your home remotely, show you energy consumption in real-time, and can even adjust themselves based on ambient conditions like humidity.
For example, you can tell them to shut off after you leave the house for work, and then spring back into action in just enough time to make the house nice and toasty (or cool and comfortable, depending on the season) by the time you to get home.
Most smart thermostats show you how long it takes to make the change you’ve requested, so you can see how effective your climate control system really is, and it discourages people from turning a thermostat all the way down to try “cooling off the house faster” (which never works). Plus, you can manage many smart thermostats from your phone or a webapp. From the remote interface, you can always see how much you’re spending on heating or cooling costs, tweak the programming to you save money, and see the results immediately.