What Size Wire for a Heat Pump?
Wire and breaker sizing for a Heat Pump — the typical 240V circuit, plus the code details (NEC Article 440) that change the answer.
Calculations are built on the 2023 National Electrical Code (NEC) and cross-checked against the published code tables. How we verify. Last reviewed June 2026.
On a 40A 240V circuit at 75°C terminations. 60°C terminations: 8.
Protected by a 40A breaker (NEC 240.6).
Heat Pump current varies by model. The size above is the common case — always size the conductor to the unit’s nameplate rating / Minimum Circuit Ampacity (MCA) and protect it at the labeled maximum breaker/fuse.
Heat Pump Circuit Details
- Like AC, size the conductor to the nameplate MCA and protect at the MOCP.
- Heat pumps with electric backup strips often need a larger circuit than cooling alone — check the air-handler rating too.
- Typical compressors land on 30–60A circuits.
Long run to your heat pump?
Over distance, voltage drop can require a larger wire than the table above. See the 40A wire size by distance:
Size it for your exact install
Open the calculator pre-filled with 40A at 240V to add distance, material and temperature.