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Mini-Split Breaker Size: What Circuit Does Each Unit Need?

by Dua Jones May 29, 2026

Every mini-split requires its own dedicated electrical circuit with a breaker sized to match the unit's electrical specifications. Using the wrong breaker size — or sharing the circuit with other appliances — causes nuisance tripping, potential equipment damage, and code violations. This guide covers exactly how to determine the correct breaker size for any mini-split and what to tell your electrician before installation.

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Key Electrical Specifications on the Nameplate

Every mini-split outdoor unit has a metal nameplate that lists the electrical specifications. Before ordering a circuit, find these two numbers:

MCA (Minimum Circuit Ampacity): The minimum wire and breaker capacity required. Your electrician sizes the wire to this number.
MOP (Maximum Over-current Protection) or MOCP: The maximum breaker size permitted. Never install a breaker larger than this number.

The correct breaker is at or above MCA but never above MOP. Electricians use the next standard breaker size above MCA (e.g., if MCA is 17A, use a 20A breaker — the next standard size).

Typical Breaker Sizes by Mini-Split BTU

BTU Capacity	Typical Voltage	Typical MCA	Common Breaker Size
9,000 BTU	208–230V	10–12A	15A double-pole
12,000 BTU	208–230V	12–15A	15–20A double-pole
18,000 BTU	208–230V	15–20A	20–25A double-pole
24,000 BTU	208–230V	18–25A	25–30A double-pole
36,000 BTU	208–230V	25–35A	35–40A double-pole

Note: These are typical ranges. Always use the MCA and MOP from your specific unit's nameplate — actual values vary by brand, model, and efficiency rating. Never rely on BTU size alone to determine breaker size.

Why a Dedicated Circuit Is Required

A dedicated circuit means the breaker serves only the mini-split — no other outlets, lights, or appliances share it. This is required by the National Electrical Code (NEC) in the US and the Canadian Electrical Code (CEC) because:

The mini-split draws significant starting current (inrush) that could trip a shared breaker
Other loads on the circuit could cause voltage drops that affect the mini-split's control boards
Code compliance and equipment warranty both require a dedicated circuit

Canadian Electrical Code Note

In Canada, the same MCA/MOP approach applies. Canadian electrical panels use similar double-pole breakers for 240V circuits. Canadian systems typically use 240V (not the US 208–230V range) — confirm your unit is rated for Canadian voltage or buy a Canadian-market unit to ensure compatibility.

Frequently Asked Questions

Can I use an existing outlet circuit for a mini-split?

No — mini-splits require a dedicated 240V circuit, not a standard 120V household outlet circuit. Even if a 240V circuit exists (e.g., for a dryer), sharing it with the mini-split is not code-compliant and risks both tripping and equipment damage. A new dedicated circuit must be run from the main panel to the outdoor unit location.

What wire gauge does a mini-split need?

Wire gauge is determined by the MCA value. Common sizes: MCA up to 15A → 14 AWG; MCA up to 20A → 12 AWG; MCA up to 30A → 10 AWG; MCA up to 40A → 8 AWG. Your licensed electrician determines the correct gauge based on the MCA, the run length, and local code requirements. Always use a licensed electrician for mini-split wiring — this is not a DIY task.