The type you need depends on your panel, your voltage, and what you're protecting

The circuit breaker you install must match three things: the amperage you need, the voltage your home runs on, and the physical space in your panel. Most homes use a 120/240-volt main panel and need either single-pole breakers (for 120-volt circuits) or double-pole breakers (for 240-volt circuits). The amperage rating — 15, 20, 30, 50 amps, and so on — must match the wire gauge of the circuit it protects. Installing the wrong breaker can damage equipment or create a fire hazard.

Before you buy anything, you need to know what panel you have. The manufacturer's name is stamped on the inside of your panel door. Common brands include Square D, Siemens, General Electric, and Eaton. Breakers are not interchangeable between manufacturers — a Square D breaker will not fit safely in a Siemens panel. If you do not know your panel brand, a licensed electrician can identify it in minutes.

Key Takeaways

  • Single-pole breakers protect 120-volt circuits and take up one slot in your panel; double-pole breakers protect 240-volt circuits and take up two slots.
  • The amperage rating (15, 20, 30 amps, etc.) must match the wire gauge running that circuit — using a higher-amp breaker on thinner wire is a fire risk.
  • Breakers are manufacturer-specific: Square D breakers do not fit Siemens panels, and mixing brands voids warranties and creates safety problems.
  • Most standard breakers cost between $15 and $40 each, but specialty breakers like AFCI or GFCI types run $40 to $100 and are required in certain rooms by code.

Single-pole versus double-pole breakers

A single-pole breaker protects one 120-volt circuit and occupies one slot in your panel. These are the most common breakers in residential homes and typically come in 15-amp or 20-amp ratings. They control circuits that power outlets, lights, and small appliances in most rooms. If the circuit draws too much current, the breaker trips and cuts power to that circuit only.

A double-pole breaker protects one 240-volt circuit and occupies two adjacent slots in your panel. These are used for high-power appliances like electric ranges, water heaters, dryers, and air conditioning units. Double-pole breakers come in higher amperage ratings — typically 30, 40, 50, or 60 amps — because they handle the larger power draw those appliances need. When a double-pole breaker trips, it cuts power to both legs of the 240-volt circuit simultaneously.

Your home's main breaker is also a double-pole breaker, usually rated 100, 150, or 200 amps depending on your home's total electrical capacity. This breaker controls all power entering your home and is the last line of defense if something goes seriously wrong with your electrical system.

Matching amperage to wire gauge

The amperage rating of your breaker must never exceed the capacity of the wire it protects. Wire comes in different gauges, and each gauge has a maximum safe current. 14-gauge wire can safely carry 15 amps, so it must be protected by a 15-amp breaker. 12-gauge wire can carry 20 amps and needs a 20-amp breaker. 10-gauge wire can carry 30 amps and needs a 30-amp breaker. Using a 20-amp breaker on 14-gauge wire means the wire can overheat and start a fire before the breaker trips.

If you are adding a new circuit or replacing an existing one, the wire gauge is already in place. Your job is to match the breaker to that wire. If you do not know what gauge wire is in a particular circuit, a licensed electrician can check it by opening the panel and looking at the wire itself or by tracing it back to its source. Never guess — an incorrect match is a genuine fire hazard.

Larger appliances use thicker wire and higher-amp breakers. A 240-volt electric range typically uses 6-gauge or 8-gauge wire with a 40-amp or 50-amp breaker. A 240-volt water heater might use 10-gauge wire with a 30-amp breaker. The circuit design — wire, breaker, and appliance — is engineered as a unit, and changing one part without changing the others creates danger.

Standard breakers versus specialty types

Standard thermal-magnetic breakers are the most common type. They trip when current exceeds their rating or when they detect a short circuit. They cost $15 to $40 each and work for most household circuits.

AFCI breakers (arc-fault circuit interrupters) detect dangerous electrical arcs — the kind that can start fires — and trip faster than standard breakers. Building codes now require AFCI protection in bedrooms, living rooms, kitchens, and other living spaces. They cost $40 to $80 each. Some panels accept AFCI breakers directly; others require a separate AFCI outlet downstream of a standard breaker.

GFCI breakers (ground-fault circuit interrupters) protect against shock hazards in wet areas like bathrooms, kitchens, and outdoor circuits. They trip if they detect current leaking to ground — a sign someone might be getting shocked. GFCI breakers cost $40 to $100 each. Like AFCI, some panels accept them as breakers, and others require GFCI outlets instead.

Combination AFCI/GFCI breakers exist but are expensive and less common. Many electricians use standard breakers paired with AFCI or GFCI outlets in the circuits themselves, which is often cheaper and easier to troubleshoot if something fails.

Finding your panel brand and checking available space

Open the door of your electrical panel and look for the manufacturer name stamped on the inside. Square D, Siemens, General Electric, Eaton, and Cutler-Hammer are the most common in North America. Write this down — it is the only information you need to buy the correct breaker.

While the panel is open, count how many empty slots are available. Each single-pole breaker takes one slot; each double-pole breaker takes two adjacent slots. If your panel is full, you cannot add new breakers without upgrading the entire panel, which requires a licensed electrician and a permit. If you have empty slots, note how many so you know what you can add.

Some older panels have tandem breakers — two thin breakers that fit in one slot — but these are controversial and not allowed in all jurisdictions. If your panel has them, do not add more without checking your local electrical code first.

Cost and where to buy

Standard single-pole breakers cost $15 to $30 at home improvement stores and electrical supply shops. Double-pole breakers run $20 to $40. Specialty breakers like AFCI or GFCI types cost $40 to $100. Prices vary by brand and retailer, but the difference between the cheapest and most expensive option is usually under $50 per breaker.

Buy from a home improvement store, an electrical supply shop, or online. Make sure you have the correct manufacturer name and amperage rating before you check out. If you are unsure, bring a photo of your panel or the breaker you are replacing, and a store employee can confirm you have the right part.

If you are not comfortable working inside an electrical panel yourself, hire a licensed electrician. The cost of installation is typically $100 to $300 per breaker, depending on your area and the complexity of the work. This is money well spent — working inside a live panel is dangerous, and mistakes can cause fires or electrocution.

Frequently Asked Questions

Can I use a breaker from a different manufacturer if it is the same amperage?

No. Breakers are designed to fit only their own manufacturer's panels. A Square D breaker will not fit safely in a Siemens panel, even if the amperage matches. Forcing it in can damage the panel, create loose connections, and cause fires. Always match the breaker brand to your panel brand.

What happens if I put a 20-amp breaker on 14-gauge wire?

The wire can overheat and melt its insulation before the breaker trips, potentially starting a fire inside your walls. The breaker is designed to protect the wire, not the appliance. Using a higher-amp breaker than the wire can handle defeats that protection. Always match the breaker amperage to the wire gauge.

Do I need an AFCI breaker or an AFCI outlet?

Building code requires AFCI protection in certain rooms, but it does not specify whether you use a breaker or an outlet. An AFCI breaker protects the entire circuit. An AFCI outlet protects only outlets downstream of it. AFCI breakers are more expensive but simpler; AFCI outlets are cheaper but require one outlet per circuit. Ask your electrician which approach your local code prefers.

Can I add a breaker to my panel myself?

Technically, yes — the panel is not locked. Practically, no. Working inside a live electrical panel is extremely dangerous. Even with the main breaker off, some parts remain energized. A licensed electrician knows how to work safely and will pull the required permit. The cost is worth the safety.

What amperage breaker do I need for a new outlet?

It depends on what you are plugging in. Most household outlets are on 15-amp or 20-amp circuits. A 15-amp breaker is standard for lights and low-power devices. A 20-amp breaker is standard for kitchen counters, bathrooms, and general-purpose outlets. For anything larger — a window air conditioner, a space heater, a power tool — ask an electrician to size the circuit correctly.