What Size Cable Do You Need for a Hot Tub?
For a hot tub, use 6mm² cable for units up to 32A (7.4kW) or 10mm² for larger models up to 40A (9.2kW) under BS 7671. In the US, most hot tubs require a 50A GFCI circuit with 6 AWG wire per NEC Article 680. All hot tub circuits require RCD/GFCI protection.
Quick Reference: Cable Size for Hot Tub / Spa by Standard
| Standard | Cable Size | Conditions | Reference |
|---|---|---|---|
| BS 7671 | 6mm² to 10mm² | Outdoor circuit, RCD protected, BS 7671 Section 702 | Table 4D1A |
| NEC | 6 AWG | 50A GFCI circuit, NEC 680 | Table 310.16 |
| AS/NZS 3008 | 6mm² to 10mm² | Outdoor, RCD protected | Table 13 |
| IEC 60364 | 6mm² to 10mm² | Section 702 requirements | 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 Hot Tub / Spa
- Inflatable hot tub
- Hard-shell hot tub
- Swim spa
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
Can I plug a hot tub into a normal socket?▼
Small inflatable hot tubs (under 2kW) can use a standard 13A socket with RCD protection. Larger hard-shell hot tubs (3-9kW) require a dedicated circuit — never use a plug and socket for these.
Does a hot tub need RCD protection?▼
Yes. Under BS 7671 Section 702 (swimming pools and hot tubs), 30mA RCD protection is mandatory. NEC Article 680 requires GFCI protection for all hot tub circuits.
What size cable for a 13 amp hot tub?▼
A 13A hot tub (under 3kW) can run on a standard 13A socket via a 2.5mm² ring final circuit. However, a dedicated radial circuit is recommended for reliability and safety.
How far can I run cable to a hot tub?▼
On 6mm² at 32A, maximum run for 5% voltage drop is approximately 25m. For 10mm² at 40A, approximately 27m. Most garden installations are well within these limits.
Do I need an electrician to install a hot tub?▼
Yes, in the UK. Hot tub installation is notifiable work under Building Regulations Part P. A qualified electrician must install the dedicated circuit, RCD protection, and issue an electrical installation certificate.
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