An electric space heater can be an efficient way to heat a room because it heats only where you want, not the entire house. When shopping for a space heater, the Department of Energy recommends you buy one that has the Underwriters Laboratory (or UL) label on it, which means it has passed certain safety tests. Choose one that has a thermostat on it; this allows you to choose the right heat settings for your home so you're not overheating a room. Be sure to keep space heaters away from automatic thermostats in your home -- it could trick the thermostat into thinking your whole home is warmer than it is. Finally, get the right size: Measure the room and use the space chart on the box to find the right size at the store.