A space heater can make sense when you want one room warm and are willing to let the rest of the house stay cooler. Think of it as a targeted tool. Warming the room you are actually in, such as a home office during the workday, can cost less than heating every room to the same temperature.

The savings disappear, however, if you run several space heaters while the central heat stays at its usual setting. Electric resistance heaters can draw a lot of power, so using them throughout the house may actually push your bill higher. The strategy only works when you lower the main thermostat at the same time.

Safety comes first. Choose a heater with tip-over protection and automatic shutoff, plug it directly into a wall outlet rather than an extension cord, and keep it well away from bedding, curtains and furniture. Never leave a space heater running while you sleep or when you leave the room.