Quick answer
A heat pump electrical circuit is the dedicated branch circuit, usually 240 volts, that powers a heat pump’s outdoor unit, sized from the unit’s nameplate minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP).
MCA sets the smallest wire allowed. MOCP sets the largest breaker or fuse allowed. A disconnect near the unit and, in many systems, a second circuit for backup heat complete the picture.
Quick facts
The key facts about Heat Pump Electrical Circuit, with sources:
- Wire sized from
- MCA on the nameplate 2
- Breaker no larger than
- MOCP on the nameplate 2
- Example (12,000 Btu/h mini-split)
- MCA 10 A, MOCP 15 A, recommended breaker 15 A 1
- Efficiency
- Up to 3× more heat than the electricity used (ENERGY STAR) 3
Key takeaways
- A heat pump’s circuit is set by two nameplate numbers: MCA for the wire and MOCP for the breaker.
- The breaker must not exceed MOCP, and the wire must carry at least MCA.
- Many home units run on 208/230-volt single-phase power, which means a 2-pole breaker.
- Ducted systems with electric backup heat often need a second, larger circuit for the air handler.
- The 2026 NEC changed GFCI rules for outdoor HVAC equipment; your inspector applies the edition your area uses.
What the term means
A branch circuit is the wiring from one breaker to the things it powers. A heat pump circuit is the one that feeds the outdoor unit, where the compressor and fan live. It serves nothing else, so it is a dedicated circuit.
Heat pumps move heat instead of making it. ENERGY STAR says an air-source heat pump can deliver up to three times more heat to a home than the electricity it uses 3.
DOE says modern air-source units can cut electricity used for heating by 50% compared with furnaces and baseboard heaters 4. That efficiency still needs a properly sized circuit.
Unlike a lamp or toaster, a heat pump has a motor that pulls a surge of current at start-up. That is why its circuit is sized from the maker’s numbers, not from a simple watts-to-amps sum.
How MCA and MOCP set the circuit
Mitsubishi Electric explains MCA as the highest steady current the unit should see when running correctly. It is used to pick the minimum wire size, so the wire will not overheat under expected conditions 2.
MOCP, sometimes printed MOP or “max fuse,” is the largest breaker or fuse that may protect the circuit 2. It is bigger than MCA on purpose, so the breaker does not trip each time the compressor starts.
In short, MCA is the floor for the wire, and MOCP is the ceiling for the breaker. The electrician picks a breaker at or below MOCP and a wire rated at or above MCA, then checks run length for voltage drop.
Wire ampacity ≥ MCA and Breaker rating ≤ MOCP
MCA- Minimum circuit ampacity, from the nameplate; sets the smallest wire
MOCP- Maximum overcurrent protection, from the nameplate; sets the largest breaker or fuse
Breaker rating- Chosen between MCA and MOCP, often the maker’s recommended size
Source: [2]
Circuits by heat pump type
| System | Circuits usually involved | Notes |
|---|---|---|
| Ductless mini-split, single zone | One 240-volt circuit to the outdoor unit; indoor head fed through the interconnect cable | The example unit powers indoor and outdoor from one supply 1 |
| Multi-zone mini-split | One circuit to the outdoor unit serving several heads | Larger MCA than a single zone |
| Ducted air-source heat pump | Outdoor unit circuit plus an air handler circuit | Electric backup heat strips can need a large separate circuit |
| Ground-source (geothermal) | Indoor unit circuit, plus pumps for the ground loop | Sized from the maker’s data |
| Heat pump water heater | Usually its own 240-volt circuit | See electric water heating research |
Example: reading a real mini-split nameplate
Mitsubishi’s submittal for the MSZ-FS12NA / MUZ-FS12NA 12,000 Btu/h mini-split lists these electrical values 1:
| Nameplate item | Value | What it means for the circuit |
|---|---|---|
| Voltage, phase, frequency | 208/230 V, 1 phase, 60 Hz | 2-pole breaker on a 240-volt branch circuit |
| Guaranteed voltage range | 187–253 V | Works on 208 V or 240 V services |
| MCA | 10.0 A | Wire must be rated for at least 10 A |
| MOCP | 15 A | Breaker may not exceed 15 A |
| Recommended breaker (outdoor) | 15 A | The maker’s choice, at the MOCP limit |
| Efficiency | SEER 26.1, HSPF 12.5 | Not used for sizing, but shows why it is efficient |
So this unit gets a 15-amp 2-pole breaker and wire rated above 10 amps, sized up for the run and local code. Other models differ, sometimes a lot, so never size a circuit from Btu/h alone. Check the run with the voltage drop calculator.
Where to find these numbers
The nameplate on the outdoor unit lists voltage, phase, MCA and MOCP. Mitsubishi says these values appear on the data plate 2. The submittal sheet and installation manual list them too.
On an HVAC quote, ask for the model number and whether the price includes the electrical work. On the panel, the breaker label should name the heat pump. Our appliance circuit lookup shows typical circuits for common loads.
Why sizing it right matters
A right-sized circuit
- Starts the compressor without nuisance trips.
- Keeps the wire cool under long run times.
- Matches the maker’s warranty and install terms.
- Passes inspection the first time.
A wrong-sized circuit
- A breaker above MOCP may not protect the unit or wire.
- Wire below MCA can overheat.
- Long runs on small wire cause voltage drop and poor performance.
- Unplanned backup heat can overload the panel on cold mornings.
What the nameplate does not tell you
The nameplate sizes one circuit. It does not tell you whether your panel has room. That needs a load calculation of the whole home, which may point to a panel upgrade if you are adding several electric loads at once.
It also does not cover backup heat on ducted systems. ENERGY STAR notes pairing a heat pump with a backup source heats most efficiently in the coldest weather 3; if that backup is electric, it has its own circuit.
What drives the electrical cost
No prices here. These drive the electrical part of a heat pump job; see the project cost tool for current ranges.
- Number of circuits: outdoor unit, air handler, backup heat.
- Run length from panel to unit.
- Panel room for 2-pole breakers.
- Disconnect and whip at the outdoor unit.
- Service capacity, if a load calculation shows you are short.
- Lifespan and warranty follow the equipment maker’s terms; correct wiring is often a warranty condition.
How the circuit gets installed
- The HVAC contractor picks the model and shares the submittal.
- An electrician runs a load calculation and checks panel space.
- Permits are pulled; some areas need both a mechanical and an electrical permit.
- The electrician installs the breaker, wire, disconnect and connection to the unit.
- The inspector checks wire and breaker against MCA and MOCP.
- The HVAC contractor starts up the system.
Keeping the circuit healthy
Keep plants and snow clear of the outdoor disconnect. Make sure the panel label names the heat pump breaker.
If the breaker trips, you may reset it once. If it trips again, leave it off and call for service, since the cause may be the unit or the wiring.
Warning signs
- The heat pump breaker trips more than once.
- Lights dim hard when the compressor starts.
- Burn marks or a hot smell at the outdoor disconnect.
- A breaker label that does not match the unit’s MOCP.
- Backup heat that trips the main breaker on cold mornings.
Safety
Safety and risk
The outdoor disconnect still has live parts on the supply side. Do not open it, swap fuses or rewire it. Reset a tripped breaker once at most; call a licensed electrician for anything more.
Code rules that apply
NEC Article 440 covers air-conditioning and refrigeration equipment, including heat pumps. Several 2026 changes touch heat pump circuits, according to Minnesota’s code review 5:
210.8(F): the GFCI threshold for outdoor outlets rose from 50 to 60 amps for single-phase circuits of 150 volts or less to ground, and a new exception permits a listed Class C SPGFCI for listed HVAC equipment.
440.11: doors or covers that expose live parts on HVAC disconnects must be locked or need a tool. An informational note introduces high-frequency breakers to cut nuisance trips from variable-speed HVAC 5.
Which edition your inspector uses depends on adoption; look up your area’s edition.
State factors that change a heat pump circuit
Two state variables matter. The code edition sets the GFCI and disconnect rules: Minnesota applies the 2026 NEC to permits filed from 17 August 2026 6.
And state rebate programs can fund the wiring: Washington’s HEAR program covers electric panel and wiring upgrades needed for new electric equipment for eligible households 7.
Rules and funding vary by state; read our incentives guide for status.
Compared with related circuits
| Circuit | How it is sized | Load type |
|---|---|---|
| Heat pump circuit | Nameplate MCA and MOCP | Motor load with start surge |
| EV charger circuit | 125% of charger current | Continuous, steady |
| Electric range circuit | Nameplate and NEC load rules | Cycling heating elements |
| General dedicated circuit | Load and code minimums | Varies |
Common misconceptions
- Myth Size the breaker from the Btu rating.
- Reality Use the nameplate MCA and MOCP; models with the same Btu rating can differ.
- Myth Bigger breaker means safer.
- Reality A breaker above MOCP breaks the maker’s rules and may not protect the wire.
- Myth Heat pumps always need a 200-amp service.
- Reality Many fit existing services; a load calculation decides.
What to check before you buy
- Ask for the submittal sheet and read MCA, MOCP and voltage.
- Ask whether backup heat is electric and how big its circuit is.
- If you are also adding an EV charger or induction range, ask for one load calculation covering all of them.
- Next step: run the electrification readiness check.
Get the model number first
Electricians cannot price a heat pump circuit well without the model. Send them the submittal sheet with your request.
Questions about Heat Pump Electrical Circuit
What size breaker does a heat pump need?
Whatever the nameplate allows: no larger than the MOCP (maximum overcurrent protection). For example, Mitsubishi’s MUZ-FS12NA lists MOCP of 15 amps and recommends a 15-amp breaker. Other units differ, so always read the nameplate or submittal for your model.
What is MCA on a heat pump?
MCA is minimum circuit ampacity. Mitsubishi describes it as the highest steady current the unit should see when working correctly, used to choose the minimum wire size. The wire feeding the unit must be rated to carry at least the MCA.
What is MOCP or MOP?
MOCP, also printed MOP or max fuse, is maximum overcurrent protection: the largest breaker or fuse allowed on the unit’s circuit. It sits above MCA so the compressor can start without tripping the breaker.
Does a heat pump need a dedicated circuit?
Yes. The outdoor unit is fed by its own branch circuit sized to its nameplate. Ducted systems often need a second circuit for the air handler and any electric backup heat.
Do heat pumps need 240 volts?
Most whole-home and mini-split units in the U.S. run on 208/230 volts single phase. The example Mitsubishi unit lists 208/230 V with a range of 187 to 253 V. Some small units run on 120 volts; the nameplate tells you.
Will a heat pump require a panel upgrade?
Not always. A load calculation of the whole home decides. Homes adding a heat pump, EV charger and induction range together are more likely to need one, and load management can sometimes help.
Do heat pumps need GFCI protection?
Heat pump GFCI rules depend on your code edition. The 2026 NEC raised the 210.8(F) outdoor GFCI threshold from 50 to 60 amps and allowed a listed Class C SPGFCI for listed HVAC equipment. Your inspector applies the edition your area adopted.
Why does my heat pump breaker keep tripping?
Causes include a failing compressor or fan, a loose connection, an undersized breaker or a ground fault. Reset it once. If it trips again, leave it off and call an HVAC technician or electrician, because repeated resets can damage the unit.
Can I wire a heat pump myself?
We do not recommend it. The work involves the panel, a 240-volt circuit and an outdoor disconnect, and usually needs a permit and inspection. Hire a licensed electrician to do the wiring.
Sources
- Mitsubishi Electric, submittal data MSZ-FS12NA / MUZ-FS12NA, retrieved .
- Mitsubishi Electric Sales Canada, MCA and MOP/MOCP Explanation (2020), retrieved .
- ENERGY STAR, Air Source Heat Pumps, retrieved .
- U.S. Department of Energy, Pump Up Your Savings with Heat Pumps, retrieved .
- Minnesota DLI Board of Electricity, NEC 2026 Adoption Review Committee minutes (25 Sep 2025), retrieved .
- Minnesota Department of Labor and Industry, Electrical contractors and the 2026 NEC, retrieved .
- Washington Department of Commerce, Home Electrification and Appliance Rebates (HEAR), retrieved .
Expert review
Written by the HyreElectrical Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: MCA and MOCP definitions are from Mitsubishi Electric’s explanation; example values are read from the MSZ-FS12NA/MUZ-FS12NA submittal. Efficiency claims are from ENERGY STAR and DOE. 2026 NEC changes are from Minnesota DLI committee minutes; adoption date from Minnesota DLI; rebate scope from Washington Commerce.
Suggest a correction. We fix errors and say what changed.