More than just hot and cold...

“On average, a programmable thermostat can save you $180 per year. Programmable thermostats come in different models that can be set to fit your weekly schedule. Additional features of programmable thermostats can include indicators for when to replace air filters or HVAC system problems, which also improve the efficiency of your heating and cooling system.”

https://www.energysage.com/energy-efficiency/101/ways-to-save-energy/