What component can significantly affect the efficiency of an electric heater?

The placement of the thermostat is a critical factor in determining the efficiency of an electric heater. A thermostat controls the temperature of the environment by turning the heating system on and off. If the thermostat is poorly placed—for instance, located in a drafty area or near a heat source—it may not accurately sense the actual room temperature. This can lead to either over or under-heating a room, causing the system to work harder than necessary, which decreases its overall efficiency.

A well-placed thermostat should be in a location that is representative of the room's overall temperature, away from direct sunlight or drafts. Proper positioning allows for more accurate readings and better control of the heating system, ultimately enhancing its efficiency and reducing energy consumption. Thus, the role of thermostat placement is vital in optimizing the performance of electric heaters, making this the correct choice.