Manual thermostats control the furnace by turning it on and off to meet the setting the thermostat is set to. They typically have an analog dial and are not automated in any way. Most of these thermostats are being replaced by digital programmable ones due to the desire for more energy saving measures. One of the simplest ways to save money on heating and cooling is by setting the thermostat back when no one is home or everyone is in bed. With a manual thermostat, you have to remember to do that by hand. With a programmable thermostat, you can have your thermostat switch from comfort settings to energy-saving settings automatically.