Yes, you can change an existing switch to a dimmer switch. It is important to have a Triple Service Inc electrical expert perform this task as they will also check up on the condition of the wiring, ensure the box is large enough to safely contain the new wiring associated with your dimmer switch, and confirm that the switch is properly grounded. If you’re looking to replace an existing switch to a dimmer switch, call Triple Service Inc today to have a professional electrician take care of the job properly.