This $249 smart thermostat learns your schedule then programs itself to accommodate your needs. Users answer a few questions like the highest and lowest temperatures they'd like their house to reach when they're not home and what hours you'll be away, then Nest
sets at an energy-efficient Away temperature. Since thermostats control half of your home's energy, it turns out that when you correctly program your thermostat, you can save 20 percent on your heating and cooling bill, not to mention energy.
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