Programmable thermostats automatically adjust the temperature in your home to reduce your energy consumption. These thermostats have pre-sets that can dial back the temperature in a home by a certain number of degrees on a set schedule -- whenever its occupants are at work or asleep, for instance. You can schedule the thermostat to return the house to a comfortable temperature before you wake up or return from the office. Using a programmable thermostat can save homeowners up to 20 percent of their cooling and heating costs [source: Consumer Reports].
But the savings come from using less energy -- not the thermostat itself. One study by Florida Power and Light discovered that people using programmable thermostats actually used 12 percent more energy because they set their air conditioners to lower temperatures than those who didn't use such thermostats [source: Lopes, Patrick]. In 2009, the Environmental Protection Agency suspended Energy Star certification for programmable thermostats partially because of lack of evidence that the devices save money. But the takeaway is that programmable thermostats simply automate a practice that saves you money: reducing consumption of heating and air conditioning in your home.