A heat pump needs its own dedicated circuit, a breaker sized to the unit's nameplate, a disconnect within sight of the outdoor unit, and a main panel with enough spare capacity for the whole house on its coldest day. Most residential units draw somewhere between 15 and 60 amps depending on size and design, but the number that matters is printed on your specific unit, not in a general chart. In Maine, a licensed electrician makes the connection.
This guide walks through each piece in the order your installer will check it: the nameplate, the breaker, the wire, the disconnect, the panel, and the Maine rules that sit on top.
TL;DR
- Size the breaker and wire from the nameplate (MCA and MOP), never from tonnage alone. A 3-ton unit can draw anywhere from 16 to 30 amps depending on design.
- Yes, a heat pump gets a dedicated circuit, plus a disconnect within sight of the outdoor unit.
- A breaker that looks oversized for the wire is often code-compliant for HVAC equipment, because the nameplate sets the limit.
- The real question is your whole panel: homes with under 100A service or older wiring often need a load calculation, and sometimes a service upgrade.
- In Maine, the connection work goes to a licensed Master or Journeyman electrician under the 2026 NEC.
Table of Contents
- How many amps does a heat pump draw?
- Breaker size: why it can look too big
- Do you need a dedicated circuit?
- Will your electrical panel handle it?
- Maine rules: code, licensing, permits
- Perspective: what we see in Maine homes
- A pre-install electrical checklist
- Where we fit in
- Common electrical problems after installation
- FAQ
- Sources
How many amps does a heat pump draw?
The range is wide. A service bulletin from an HVAC equipment maker puts residential heat pump draw at roughly 15 to 60 amps, and notes that a 3-ton unit may draw anywhere from 16 to 30 amps depending on its technology and operating conditions. The same document says a 1.5-ton unit may call for a 15 to 20 amp breaker, while a 5-ton unit can need up to 60 amps.
That spread is why a chart on a website cannot size your circuit. Two units of the same tonnage can differ by a factor of two. An inverter-driven cold-climate model ramps its compressor up and down, so it often runs well below its maximum for most of the season. A single-stage unit runs at full output whenever it runs.
There are three numbers to know, and all of them sit on the nameplate on the outdoor unit:
| Nameplate term | What it means | What it decides |
|---|---|---|
| RLA (rated load amps) | Current the compressor draws at rated conditions | Feeds the MCA calculation |
| MCA (minimum circuit ampacity) | Minimum current the wire must be able to carry | Wire gauge |
| MOP (maximum overcurrent protection) | Largest breaker or fuse allowed | Breaker size |
The NEC Article 440 formula for MCA is 125% of the compressor RLA, plus the fan motor current, plus any auxiliary heat amps. You do not need to run the math yourself, since the manufacturer already did it and printed the result. But it explains why a heat pump with backup electric resistance strips has a much bigger circuit than the same unit without them.
Breaker size: why it can look too big
Homeowners and even some inspectors see a 30 or 40 amp breaker feeding a wire that would be limited to a lower rating on a lamp circuit and assume something is wrong. Usually nothing is.
HVAC compressors are treated differently from ordinary branch circuits. InterNACHI explains that the IRC and NEC provide an exception to the general rule linking breaker rating to wire size, and that compressor motors carry built-in thermal protection for overloads. The breaker's main job on these circuits is short-circuit and ground-fault protection. Starting current can also be several times the running current, which the unit's electronics and capacitors manage.
The practical rules:
- Never exceed the MOP printed on the nameplate. That is a hard ceiling. The same manufacturer bulletin says breaker sizing must never go above it.
- Never go below what the unit needs to start and run. A breaker that trips on every compressor start is undersized for the MCA, not a sign of a faulty heat pump.
- Match the wire to the MCA, not to the breaker. The wire gauge follows the ampacity the unit needs.
- Use the specific model's data. If you replace a unit, the old breaker is not automatically right for the new one. A change-out is a good moment to recheck.
If you want a second opinion on a breaker that looks wrong, ask the electrician to show you the nameplate MCA and MOP and the wire gauge side by side. A competent installer will do that in a minute.
Do you need a dedicated circuit?
Yes. A heat pump condenser should sit on its own circuit, with nothing else sharing it. A compressor and fan motor start under load and run for hours, and any other device on the same line would face voltage dips and nuisance trips. Multi-zone systems may add a separate circuit for indoor units depending on the manufacturer's wiring design, so check the installation manual for the exact arrangement.
Three pieces make up a proper circuit:
- Breaker in the panel, sized to the nameplate MOP.
- Wire sized to the MCA, run in the proper conduit or cable type for the location.
- A disconnect within sight of the outdoor unit. A federal permitting checklist for heat pump space heating lists a dedicated disconnect within sight of the outdoor unit as a requirement, rated for the equipment's load under NEC Section 440, so power can be cut quickly during service or an emergency.
The same checklist covers the physical setup around the electrical work: a stable, level, non-wicking pad or stand that lifts the unit above snow, ice and flood lines, and manufacturer clearances on all sides so airflow is not blocked. In Maine, that stand height matters as much as the wiring. A unit buried by drifts is not just inefficient, it can be damaged. Our piece on mini split placement mistakes covers the location side in detail.
Will your electrical panel handle it?
This is where most surprises come from. The heat pump circuit itself is simple. The question is whether the house has capacity left once the heat pump is running during a cold snap, with the range, dryer, water heater and well pump all possibly in use.
New York's clean heat program, in its installer guidance, notes that heat pumps often increase amperage, so the home's electrical system capacity must be assessed before installation. It is a New York document, but the physics and the NEC are the same in Maine. Installer experience points the same way: homes built before about 1965 or with service under 100 amps are the likeliest to need an upgrade, and a full load calculation beats guessing.
A few points that save homeowners money:
- A visual check is not enough. Looking at the panel label tells you the main breaker size, not how much of it you are using. Ask for a load calculation from a licensed electrician.
- You may not need 200 amps. A larger panel is not automatically required. Many homes with efficient mini splits fit within existing service once the calculation is done, particularly where major appliances run on fuel rather than electricity. The calculation decides, not a rule of thumb.
- Backup resistance heat changes the math. If a system includes electric strip heat for extreme cold, its amps add to the circuit and to the home's peak load.
- Panel upgrades can be financed. Efficiency Maine states that electric panel and electrical service upgrades count as part of an eligible heat pump project under its home energy loans. Confirm current terms with the program before you sign anything. Our Maine heat pump rebates page is a good place to start on what applies.
When the grid or the panel is the limit
If the load calculation shows the service is tight and an upgrade is expensive or slow, there are options beyond a bigger main panel, such as load management and onsite backup or storage. One engineering firm lays out heat pump backup power options and what an engineer needs to know, which is useful reading if you are weighing capacity and outage resilience together. For most Maine homes the first step is still a proper load calculation.
Maine rules: code, licensing, permits
Two Maine-specific points matter before anyone touches a wire.
The code. The Maine Electricians' Examining Board adopted a new Chapter 120 incorporating the 2026 NEC, subject to the state's amendments. Your electrician works to that version, not an older one you may have read about online.
The license. The connection work on a heat pump must be performed by a licensed Maine electrician, Master or Journeyman. The same state page covers electrician licensing. Efficiency Maine also expects installers participating in its programs to hold the appropriate electrician license and carry required insurance, so a handyman wiring your unit can cost you the incentive as well as create a safety problem.
Two cautions on what not to do. Do not wire the unit yourself, even if you are handy; the disconnect, breaker and grounding are inspected items. And do not hire on the lowest quote alone. Installer guidance from the UK's Energy Saving Trust, a different market with different codes, makes a point that holds anywhere: electrical requirements go beyond the breaker, including grounding integrity, correct residual-current or ground-fault protection for inverter equipment, and separation of power and communication cabling. A cheap quote often leaves those out.
Perspective: what we see in Maine homes
We design cold-climate systems around heat-loss calculations, and we treat the electrical side the same way: start from the real load, not a rule of thumb. The most common mistake we see is sizing equipment by tonnage and then discovering the electrical side was never checked. A unit chosen for a cold January needs a circuit and a panel chosen for that same January.
Three habits we recommend to every homeowner:
- Ask for the nameplate MCA and MOP for the exact model before the quote is final, so the electrician prices the right circuit.
- Have the panel assessed in the same visit as the heat-loss calculation. Both answers shape the equipment choice, and a smaller, well-sized inverter system can reduce the electrical ask.
- Do not let a breaker that looks oversized alarm you, and do not let a tripping breaker be silenced by swapping in a bigger one. The nameplate is the authority both ways.
If you want the cold-weather performance side of this, our guide on planning for heat pump capacity at 5°F explains why peak load, not average load, drives both equipment and electrical decisions. And for how inverter systems are sized and commissioned, see our inverter heat pump guide.
— John
A pre-install electrical checklist
Bring this list to your first appointment:
- Main panel label: amperage rating of the main breaker and how many open slots remain.
- Service age and condition: note any scorched breakers, aluminum branch wiring, or fuse panels.
- Other big loads: electric range, dryer, water heater, EV charger, well pump, electric heat in any rooms.
- Outdoor unit location: distance from the panel, since longer runs may need heavier wire, and a spot where a disconnect can sit within sight.
- Model nameplate data: MCA and MOP for each unit under consideration.
- Backup heat plan: whether electric strips are included, and their amps.
- Permit and inspection: who pulls the permit, and who schedules the electrical inspection.
Where we fit in
We install and replace cold-climate heat pumps across Maine, sized from heat-loss calculations, in ductless, multi-zone and ducted configurations. Service is confirmed by ZIP code before appointments or payments. If you are planning a project, our installation planning page explains the process, and the services page lists new installs and change-outs. The connection itself belongs to a licensed Maine electrician.
Once the system is running, upkeep protects both performance and the electrical side, since a dirty coil makes the compressor work harder. Our Annual Cleaning Plan is $219 per year and the Maine Heat Pump Care Plan is $319 per year. A one-time deep cleaning starts from $249.
Common electrical problems after installation
Breaker trips when the unit starts. Could be an undersized breaker relative to the MCA, a failing capacitor, or a loose connection. Do not replace the breaker with a larger one. Have a licensed electrician or technician read the nameplate and test the circuit.
Unit short cycles. Often a commissioning or sizing issue rather than electrical. See short cycling fixes.
No heat at all. Check the thermostat, the indoor breaker, and the outdoor disconnect, then call a professional. Our five checks for a heat pump that is not heating lists them in order.
Refrigerant or low output. Not an electrical fault, and not a homeowner repair; see what homeowners cannot do about recharges.
FAQ
What size breaker does a heat pump need?
It depends on the model. Use the MOP on the outdoor unit's nameplate as the maximum, and the MCA to size the wire. A small 1.5-ton unit may need a 15 to 20 amp breaker, while a 5-ton can need up to 60 amps. Have a licensed electrician confirm it against your exact model.
Does a heat pump need a dedicated circuit?
Yes. The outdoor unit should run on its own circuit, with a disconnect within sight of it. Sharing the circuit with other loads risks nuisance trips and violates the equipment's wiring requirements.
Can a 100-amp panel run a heat pump?
Often, yes, but only a load calculation can say. Homes with 100-amp service, older wiring, or large electric loads like a range, dryer and EV charger are the ones most likely to need an upgrade. Efficiency Maine lists panel and service upgrades as eligible in its heat pump loans.
Can I wire a heat pump myself in Maine?
No. Electrical connection work must be done by a licensed Maine electrician, Master or Journeyman, under the 2026 NEC as adopted by the state. Doing it yourself can also put program incentives and your warranty at risk.
Why is my breaker bigger than the wire seems to allow?
HVAC equipment follows NEC Article 440, which allows a higher breaker rating because the compressor has its own overload protection. Check that the breaker does not exceed the nameplate MOP and the wire meets the MCA.
Sources
- GEDi service bulletin: heat pump max breaker (MOP) by tonnage
- VoltageLab: HVAC and heat pump circuit calculator (NEC Art. 440)
- InterNACHI: inspecting oversized breakers on small-gauge wires
- U.S. DOE: heat pump space heating permitting and inspection checklist
- NYS Clean Heat: assessing residential electrical service
- Efficiency Maine: home energy loans
- Maine Electricians' Examining Board
- Energy Saving Trust: guidance for electricians