Installing a motion sensor is a quick investment that will pay for itself and help you save money in the long run. As much as we hope people will remember to turn off the lights when they leave a room, it’s often forgotten. One way to help eliminate this kind of waste is to install a motion sensor in the most frequently used room in the house. A $15 sensor (available at any hardware store) will automatically turn off the lights for you when it doesn’t sense movement in a room. Home offices, family rooms and conference rooms at the workplace are great places to consider installing one.