What Size Cable Do You Need for a Heat Pump?
Heat pump cable size depends on the compressor rating. A typical 5-8kW air source heat pump draws 8-16A, requiring 2.5-4mm² cable. Larger 12-16kW units draw 20-30A, needing 6-10mm². Always size from the manufacturer's nameplate MCA (minimum circuit ampacity), not the kW heating output.
Quick Reference: Cable Size for Heat Pump by Standard
| Standard | Cable Size | Conditions | Reference |
|---|---|---|---|
| BS 7671 | 4mm² to 10mm² | Depends on compressor current, dedicated circuit | Table 4D1A |
| NEC | 10 AWG to 6 AWG | Per nameplate MCA and MOCP, NEC 440 | Table 310.16, Article 440 |
| AS/NZS 3008 | 4mm² to 10mm² | Per compressor rating, AS/NZS 3000 | Table 13 |
| IEC 60364 | 4mm² to 10mm² | Per compressor rating, IEC 60364 | Table B.52.4 |
Values shown are for copper conductors in typical domestic/commercial conditions. Actual size depends on installation method, ambient temperature, and cable length. Use our free cable sizing calculator for your exact scenario.
Typical Applications for a Heat Pump
- Air source heat pump (ASHP)
- Ground source heat pump (GSHP)
- Hybrid heat pump
Calculate Your Exact Cable Size
These are general guidelines. Your specific installation needs exact calculation accounting for cable route length, installation method, ambient temperature, and cable grouping.
Frequently Asked Questions
What size supply cable for a 12kW heat pump?▼
A 12kW ASHP typically has a compressor drawing 20-25A at 230V. Use 6mm² cable on a 32A circuit for runs up to 25m. Check the manufacturer's MCA (Minimum Circuit Ampacity) for the exact requirement.
Does a heat pump need a dedicated circuit?▼
Yes. Heat pumps must have a dedicated circuit from the consumer unit with an appropriately rated MCB/RCBO. They should not share circuits with other loads due to compressor starting currents.
What breaker size for an air source heat pump?▼
Use the MOCP (Maximum Overcurrent Protection) from the manufacturer's nameplate. Typically 20A for small units (5-8kW), 32A for medium (8-12kW), or 40A for large units (12-16kW).
Can a heat pump run on single phase?▼
Most domestic heat pumps up to 12kW run on single-phase 230V. Larger commercial units (16kW+) often require three-phase 400V supply. Check the manufacturer's specifications.
Do I need to upgrade my supply for a heat pump?▼
If your main fuse is 60A or less, adding a heat pump may exceed supply capacity. A typical ASHP adds 15-30A to your maximum demand. Contact your DNO for a supply upgrade if needed.
Related Cable Sizing Guides
Need a different calculation?
Browse all 27 free calculators →