What's the difference between a 15-amp and a 20-amp breaker?

The current at which it trips, and therefore the wire it can protect. A 15-amp breaker protects 14 AWG copper; a 20-amp breaker protects 12 AWG. You cannot substitute one for the other without changing the wire — the breaker is chosen from the conductor, not the appliance.

Can I use any brand of breaker in my panel?

No. A breaker must be listed for use in that specific panel. Physical fit doesn't establish that. Using an unlisted breaker voids the panel's listing and is a code violation, even where the breaker seems to work fine.

What is a quad breaker?

A breaker occupying two slots but providing more than two poles' worth of circuits — commonly two 120-volt circuits on the outer handles and a 240-volt pair on the inner ones, or two separate 240-volt circuits. Like tandems, they're only permitted where the panel is listed for them.

Types of Circuit Breakers in a Home Panel

Updated 2026-08-16 · 6 min read

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Nearly every residential panel is made up of eight breaker types. Being able to identify them from the outside tells you what your circuits are, what voltage they run at, and what protection they have.

Main breaker

The single largest breaker, usually alone at the top of the panel. It disconnects everything downstream, and its rating — 100, 125, 150, 200 amps — is your service size.

Some panels have no main breaker inside; these are main-lug panels, fed from a separate outdoor disconnect. In that case the service size is on the disconnect.

Note that turning the main off does not de-energize the main lugs. Those stay live, which is why work behind the deadfront is electrician work.

Single-pole breaker

One handle, one slot, connected to one bus bar → 120 volts.

The workhorse of the panel. Typically 15 or 20 amps, protecting general lighting and receptacle circuits.

Double-pole breaker

Two handles tied together, two adjacent slots, touching both bus bars → 240 volts.

The handles are physically joined so both poles open together — a requirement, because de-energizing only one side of a 240-volt circuit leaves the other side live.

Common ratings and uses:

Rating	Typical load
30 A	Electric dryer, small water heater
40 A	EV charger, some ranges, AC
50 A	Electric range, larger EV charger
60 A	Subpanel feeder, large equipment

See single-pole vs double-pole breakers for the full comparison.

What is a tandem breaker?

Two half-height handles in one slot → two independent 120-volt circuits.

Only permitted where the panel is listed for them, and often only in specific positions. See tandem breakers explained.

Quad breaker

Two slots, but more circuits than a double-pole. Designs vary — commonly two outer 120-volt circuits plus an inner 240-volt pair, or two separate 240-volt circuits.

Same listing rules as tandems: allowed only where the panel permits.

What does a GFCI breaker do?

Has a TEST button and usually a white pigtail wire (which lands on the neutral bar). Detects current leaking out of the circuit and trips at roughly 5 milliamps.

Protects people against shock. Required in wet and damp locations — bathrooms, kitchens, garages, outdoors, basements, laundry, near sinks. See GFCI vs AFCI.

You can get the same protection from a GFCI receptacle, which protects itself and everything downstream on the circuit. Cheaper, and often the practical choice for a single location.

What does an AFCI breaker do?

Also has a TEST button, and is usually labeled AFCI or "arc fault". Detects the electrical signature of arcing — a fire precursor that overcurrent protection never sees.

Protects the building. Required on most 120-volt 15- and 20-amp branch circuits serving dwelling living areas under current code. See AFCI breakers explained.

What is a dual-function breaker?

Both AFCI and GFCI in one device, labeled as such. Used where a circuit falls under both requirements — kitchens and laundry areas are the classic cases.

More expensive than either alone, which matters when a panel replacement brings 20 or 30 circuits up to current requirements. See electrical panel upgrade cost.

Quick identification table

What you see	What it is
One handle, one slot	Single-pole, 120 V
Two handles tied, two slots	Double-pole, 240 V
Two half-height handles, one slot	Tandem — two 120 V circuits
TEST button + white pigtail	GFCI
TEST button, marked AFCI	AFCI
TEST button, marked dual-function	Both
Largest breaker, alone at top	Main

Can you use any brand of breaker in a panel?

Whatever the type, a breaker must be listed for use in your specific panel. Physical fit proves nothing — several brands share mounting geometry without being listed for each other's panels.

Using an unlisted breaker voids the panel's listing, is a code violation, and creates a real risk at the bus connection, where a mismatch in contact geometry produces heat. The panel label lists the acceptable breaker catalog numbers. See breaker brand compatibility.

The ninth device in the panel: surge protection

Since the 2020 NEC, new and replaced dwelling services also require a surge protective device (NEC 230.67) — usually a Type 2 SPD mounted in or beside the panel on its own two-pole breaker. It isn't a breaker, but it lives with them and gets installed on the same visit. The full story is in whole-house surge protectors; the current devices are compared in our surge protector picks.

Type 2 whole-house SPD

Siemens BoltShield FSPD140

Check price on Amazon

Siemens' current flagship residential SPD — 140 kA, 20 kA nominal discharge, audible alarm, and the strongest warranty terms in the group.

Best for: The default whole-house pick on any brand of panel

SPD Type: Type 2 (UL 1449 5th Ed.)
Surge capacity: 140 kA
Nominal discharge (In): 20 kA
VPR: 700 V L-N / 700 V L-G / 700 V N-G / 1200 V L-L
SCCR: 200 kA
Enclosure: NEMA 4X polycarbonate
Indicators: Status LEDs + red alarm LED + audible alarm
Warranty: 10 years, $100,000 connected equipment

20 kA nominal discharge rating — comfortably above the 2023 NEC 242.10 dwelling minimum
Audible alarm and ground-reference monitoring, so a failed unit announces itself
Mounts beside any manufacturer's load center, not just Siemens panels

Successor to the discontinued FS140 — retailers still sell the old model, so check the box says FSPD140
External mount needs a knockout and a 2-pole breaker's worth of electrician time

Read the full write-up →

Code reference

The requirements behind this guide, for looking up in your adopted edition:

NEC 240.6 — standard ampere ratings
NEC 210.12 — where AFCI protection is required
NEC 210.8 — where GFCI protection is required
NEC 230.67 — surge protection on dwelling services (2020 edition onward)

Code editions and local amendments vary by jurisdiction. Confirm the adopted edition with your AHJ before relying on any specific article.

Where to go next

Frequently asked questions

Count the handles and the slots. One handle in one slot is single-pole (120 V). Two handles tied together across two slots is double-pole (240 V). Two half-height handles in one slot is a tandem. A TEST button means it's a GFCI, AFCI, or dual-function breaker — the label on the breaker says which.

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