Outlets must be placed no more than 12 feet apart on each wall, according to the National Electric Code. This rule helps ensure that there are enough outlets available.
Otherwise, homeowners would need to plug in extension cords to use all of their electrical appliances, which puts them at risk of tripping over the cords, overloading electrical circuits or even causing a fire.
Doorways and Fireplaces
If there is a doorway in the room, electrical outlets must be placed no more than six feet from the doorway. Similarly, if there is a fireplace or other structure in the wall, outlets must be placed no more than six feet from that structure.
This is a complement to the rule about spacing between outlets. Together, they are sometimes referred to as the "6/12" rule.
Height of Wall
In most cases, electrical outlets are placed about 18 inches off the floor and the switches for the outlets are placed about 48 inches above the floor. However, outlets can be placed lower or higher if needed.
The height of the wall does not affect how many outlets are placed in the room; the length of the wall and the distances from wall breaks such as doorways are the important considerations here.
The NEC rules represent minimum requirements for location of electrical outlets. Electricians may place more outlets than the minimum in a room if desired.
This decision is usually based on what the architect and the homeowner think will be needed in the room.