Tandem Breaker
A slim breaker that fits two separate 120-volt circuits into a single panel space, used to open up room in a full panel where the panel is rated to accept them.
Tandems (also called twin or cheater breakers) are legitimate where the panel manufacturer allows them: the panel label and bus design specify how many and in which slots. They are the budget answer to "my panel is full and I need one more circuit," and electricians use them routinely.
The caveats: a panel stuffed with tandems beyond its listing is a code violation and a heat problem; tandems do not exist for most 240-volt needs; and a panel that needs many of them is usually telling you it is undersized for the house. An electrician weighing tandems versus a subpanel versus a panel upgrade is doing capacity planning, not upselling.
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- Main Breaker : The single large breaker at the top of your panel that can disconnect the entire house, and whose rating (100, 150, 200 amps) defines your service size.
- Bus Bar : The rigid metal bars inside a panel that distribute power to the breakers.
- Double-Pole Breaker : A breaker occupying two panel spaces that connects across both hot bus bars to deliver 240 volts, used for dryers, ranges, AC units, EV chargers and other heavy loads.
- AFCI (Arc Fault Circuit Interrupter) : A breaker or outlet that detects the electrical signature of dangerous arcing (loose connections, damaged wires) and cuts power before the arc starts a fire.