Depending on the time of year and where you live, adjusting your thermostat to lower temperatures during the day and at night can help boost your energy savings. You can do this with a manual (old-school) thermostat, a programmable thermostat or a smart thermostat. Programmable thermostats allow you to set a schedule of temperature changes according to your family's daily patterns such as when you go to sleep, wake up, go to work/school or return home. Many programmable thermostats allow you to set a unique schedule for each day of the week with several temperature changes per day, while others may have more basic scheduling options or a limited number of temperature adjustments that can be made per day. The thermostat will keep to your schedule until you re-program it.
Smart thermostats, on the other hand, use technology to seamlessly adjust your home’s temperatures based on your schedule and preferences, so you don't have to make any manual changes. Some require you to set an initial schedule that the thermostat will adjust over time. Others don't require you to program anything and will adjust to your comings and goings automatically. Some use motion detectors to determine if people are at home or away, and most offer options to override the smart settings with custom settings if you need to. These thermostats find ways to reduce AC or heater use through incremental changes, such as turning the HVAC system off a few minutes earlier than you may have initially set the device or adjusting the preferred temperature by a couple of degrees during times when you won't notice the difference.