What size cable for an induction hob?
A typical 7.4 kW induction hob goes on a 32 A circuit, often shared with the oven. That needs at least 4 mm² twin and earth clipped direct, or 6 to 10 mm² through insulation. Always check the hob's installation instructions, as some ask for a specific circuit.
- V – Voltage
- I – Current
- R – Resistance
- P – Power
Step 1: the current, with diversity
An induction hob is a cooking appliance, so the cooker diversity rule applies: the first 10 A, plus 30 % of the rest.
- Hob alone: 7.4 kW ÷ 230 V = 32.2 A flat out. With diversity: 10 + 0.3 × (32.2 − 10) = 16.7 A.
- Hob and a 3.5 kW oven on one circuit: 10.9 kW = 47.4 A flat out, or 21.2 A with diversity.
Both fit a 32 A breaker. Even when the maths would allow a 20 A circuit for the hob alone, many makers specify 32 A, and their instructions come first.
Step 2: choose the cable for a 32 A circuit
Run lengths use the 21.2 A design current for the hob and oven together:
| How the cable is run | Smallest twin and earth for 32 A | Longest run (voltage drop) | Longer run? Next size up |
|---|---|---|---|
| Clipped direct to a wall or joist | 4 mm² (rated 37 A) | up to 49 m | 6 mm²: up to 74 m |
| Above a plasterboard ceiling, insulation up to 100 mm | 6 mm² (rated 34 A) | up to 74 m | 10 mm²: up to 123 m |
| In an insulated stud wall, touching the inner face | 6 mm² (rated 35 A) | up to 74 m | 10 mm²: up to 123 m |
| In an insulated stud wall, not touching the inner face | 10 mm² (rated 32 A) | up to 123 m | 16 mm²: up to 193 m |
Other things to check
- A cooker control switch for isolation, within easy reach but not directly above the hob.
- Check the maximum Zs for the breaker: a B32 is 1.37 Ω (Max Zs table).
Assumes 70 °C flat twin and earth (6242Y), 230 V, an MCB or RCBO, 30 °C ambient, the circuit not bunched with others, and no thermal insulation round a clipped cable. Voltage drop limit 5 % (11.5 V), BS 7671 Table 4D5 values. Grouping, heat or insulation can need a bigger cable: check with the cable size calculator. For study and estimating only; the installing electrician must design and certify the circuit.