Thermostats control half of your home's energy. So a good one is crucial for energy savings -- and a simple one, so you'll use it. The Nest is so self-programmable, it's a almost unsettling. It learns over time, so all you have to do is adjust the temperature for a few days. As the Nest "learns" what you like, it sets itself to save you money. They claim it can save you up to 20% on your heating bills.

Price: $249

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