Use more than one and have them turn lights and radios on and off in different rooms at different times and leave a car parked in the driveway. Arrange to have your lawn mowed regularly. Ask a neighbor to gather mail and newspapers or stop delivery until you return. Don't change your answering machine. Set up an expandable file to keep all instructions, notes and articles organized and handy.
Nothing beats the cost efficiency of a gas furnace.
Instead consider using a portable electric space heater. If you want to save money this season, try using an electric space heater to warm just the room you're in, instead of heating your whole house with the gas furnace. The next time you paint a room in your home write down everything about the paint you're using. First, the brand name and color used on walls and then the same for the trim and ceilings. Then years later when it's time to paint again all info will be right there when and where needed whether for you or someone else.