The single most common electrical failure on a heat pump install is under-sized conductors — not because the electrician made an arithmetic mistake, but because the plan-set at rough-in was written before the specific equipment was selected. The plan called for "heat pump HVAC" and the electrician defaulted to 30 A / 240 V. Then at rough finish, the HVAC contractor spec'd a 5-ton Bosch IDS 2.0 heat pump with 42 A minimum circuit ampacity (MCA), which forces a 60 A / 6 AWG circuit. The wire has to be pulled again, the panel breaker has to be swapped, and the schedule slips by three days.

The fix is to spec the electrical circuit against the equipment MCA/MOCP nameplate — not against a generic "heat pump" line item. This guide gives you the MCA and MOCP for the 12 most common residential heat pump configurations, the resulting conductor and breaker spec, and the disconnect BOM to make it a one-shot rough-in decision at plan release.

Every UL-listed heat pump has two nameplate values that govern the electrical roughing: MCA (minimum circuit ampacity) and MOCP (maximum overcurrent protection). These two numbers do different things and are frequently confused.

The following table covers 95% of residential heat pump configurations from 12 kBTU (1-ton mini-split) to 60 kBTU (5-ton central split). Every row includes MCA, MOCP, conductor spec, breaker SKU, and disconnect SKU. Numbers are typical values across the major manufacturers (Mitsubishi, Fujitsu, Daikin, Bosch, Trane, Carrier, Rheem, LG); check the specific unit nameplate at final spec.

NEC 440.14 requires a disconnecting means "within sight from and readily accessible" to the outdoor heat pump unit, and additionally within 50 feet of the unit. In residential practice, this means a non-fused disconnect mounted on the exterior wall within 6 feet of the condenser pad. A fused disconnect is not required (the branch breaker at the main panel provides overcurrent protection); a lockable non-fused disconnect is sufficient.

The air handler / indoor unit needs its own disconnect only if it is not on the same circuit as the compressor. Most residential heat pumps have a separate 15 A / 120 V air-handler circuit (for the ECM blower motor); a snap disconnect at the air handler (Bridgeport 78S or built-in on the unit) satisfies NEC 440.14. Full disconnects (like the DU-series) are not required at the indoor unit.

Heat pump water heaters are electrically simpler than HVAC heat pumps (single-stage compressor, no auxiliary heat strips), but the 2023 NEC added a GFCI requirement (210.8(F)) that catches builders mid-plan. Every HPWH installed on or after March 1, 2024 requires GFCI protection on the branch circuit. This adds $22 to the breaker cost (HOM230CGFI vs HOM230CP) and eliminates the option of a downstream GFCI receptacle at the water heater — which was the traditional plumber's solution.

The 30 A / 240 V circuit is standard for both 50-gal and 65-gal HPWH units. The 80-gal commercial HPWH (like the Rheem PROTPH80T2RH350) requires a larger circuit (30 A but higher MCA at 26 A). All three HPWH sizes fit on 10/2 NM-B with a HOM230CGFI breaker. Locate the disconnect within sight of the unit — a Square D DU221 (30 A non-fused, NEMA 3R) at the water heater satisfies NEC 440.14 and gives the plumber a shutoff at service.

The reason heat pump electrical roughing goes wrong is timing — the electrician arrives before the HVAC contractor has spec'd the equipment. Fix this at plan-set release by pre-selecting the HVAC equipment and locking it into the plan library. Three approaches work:

The indoor air handler on a heat pump split system needs its own 15 A / 120 V circuit for the ECM blower motor. This circuit is trivially simple electrically (14/2 NM-B, HOM115CP breaker), but it gets missed on roughly 15% of plans because the plan-set line reads "heat pump" and the electrician wires only the outdoor circuit. Fix at the plan-set: two line items on the panel schedule — "HVAC OUTDOOR" (60 A) and "HVAC INDOOR / AH" (15 A). Both circuits.

Some plans (mostly Sun Belt) use a hydronic air handler with an integrated boiler, in which case there's no separate air-handler circuit — the boiler has its own 15 A. But for heat pump plans (Zones 2–7), always spec both circuits.

A "dual-fuel" heat pump combines an air-source heat pump with an auxiliary gas furnace for cold-weather backup. The heat pump handles cooling and shoulder-season heating; the gas furnace takes over below ~30°F. Electrically, dual-fuel is identical to a single-stage heat pump (same MCA / MOCP on the compressor), but the gas furnace requires an additional 15 A / 120 V circuit for the burner controls and blower — separate from the ECM blower on the heat pump air handler.

A pure electric heat pump with heat-strip auxiliary (common in Zones 4–5 where dual-fuel is uncommon) has a different electrical impact. The auxiliary heat strips are typically 10 kW to 20 kW / 240 V and are wired on a separate circuit from the compressor. A 5-ton heat pump with 20 kW aux strips looks like this:

This is why aux-strip heat pumps push service size to 400 A in fully-electrified homes. Two mitigations: (1) load management via NEC 220.83(A)(1) — a listed relay prevents simultaneous compressor + aux strip + EVSE operation and drops the calc back into 200 A range; (2) dual-fuel with a gas backup furnace — removes the aux strip circuit entirely.

Every heat pump electrical rough-in guide we've seen focuses exclusively on the electrical circuit — the breaker, the disconnect, the whip, the wire. That's necessary but insufficient. The heat pump also requires a refrigerant line set (typically 3/8" liquid + 3/4" or 7/8" suction) routed from the outdoor unit to the indoor coil, plus a condensate drain and a low-voltage thermostat/comms cable. If those three items aren't roughed-in together with the electrical, the retrofit story falls apart — you can have the perfect 60 A / 8 AWG / DU224 stack ready to go and the homeowner will still spend $2,800 punching lineset chases through finished conditioned space.

The integrated rough-in package puts four items in the same wall chase at the outdoor equipment location:

Integrating the four items is the difference between "heat pump-ready" and "heat pump-installable." A plan that only pre-wires the electrical circuit but doesn't rough-in the lineset chase, condensate path, and low-voltage cable is still a $2,000-$3,000 retrofit cost — the electrical is 30% of the equation. The full four-item package adds $185 to $340 at rough-in (mostly the lineset chase and condensate path) and drops the retrofit cost to $250-$400 — just the equipment set, refrigerant charge, and startup.

The integrated package is a $215 add at rough-in that returns $2,870 to the homeowner (or, more importantly, to your service department's callback log) on every unit converted. On a 240-home community, if 14% convert within two years, the community-level cost delta is $51,600 in rough-in that saves $97,500 in retrofit and service costs. The math scales with conversion rate — as heat pumps take share from A/C-plus-furnace, the integrated rough-in becomes a compounding win.