Summary

The cooker circuit is one of the highest-demand circuits in a domestic property. Electric cookers and range cookers (AGA, Rayburn, Rangemaster) draw between 7kW and 20kW, requiring dedicated circuits that would overload a standard 32A ring final. The circuit must be correctly sized for the actual appliance — and since cookers are often replaced between rewire cycles, the circuit must be sized for the maximum likely appliance, not the current one.

UK household cooking has diversified: ceramic hob plus separate electric oven, range cooker (all-electric or dual-fuel gas hob + electric oven), induction hob, and microwave combinations. Each has different current demands. The most important calculation is the demand calculation per BS 7671 — not all elements of a cooker operate simultaneously at full power, so a 14kW total cooker has a much lower maximum demand than 14,000/230 = 60A.

Key Facts

  • Demand calculation — BS 7671 Appendix 15 rule: first 10A of cooker full rated current + 30% of remainder + 5A for control unit socket
  • Example: 14kW cooker = 14000/230 = 60.9A total. First 10A + 30% of (60.9-10) = 10 + 15.3 = 25.3A. Add 5A for socket = 30.3A. Use 32A MCB and 6mm² or 40A MCB and 10mm²
  • Standard cable — 6mm² T&E (two-core and earth) for demand up to ~36A, 10mm² for demand up to ~45A
  • MCB rating — 32A, 40A, or 45A depending on demand calculation and cable size
  • Cooker control unit — Double-pole switch with indicator light. Rated 45A minimum (BS 4177). Must disconnect both live and neutral
  • Socket on control unit — Permissible only if the appliance does NOT use gas. Kitchen socket within 2m of cooker is generally acceptable per BS 7671 guidance
  • Position of control unit — Within 2m of the cooker, positioned where it can be operated without reaching over the cooker. Not directly above a hob (grease contamination, heat)
  • Part P notifiable — Yes. All new cooker circuits must be notified to Building Control via a Part P competent person scheme (NICEIC, NAPIT, etc.) or Building Control application
  • Separate oven and hob — Each appliance over 3kW ideally gets its own circuit. Combined circuit with a junction box is permissible if the demand calculation supports it
  • Range cooker circuits — Many range cookers are 13kW–24kW total. Always check the appliance rating label. Demand calculation must be performed
  • Induction hob — High starting surge current. Use a Class C or D MCB for induction hobs over 7kW. Some manufacturers specify minimum circuit requirements — check the installation instructions

Quick Reference Table

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Cooker Rating Full Load Current Calculated Demand (BS 7671) Cable MCB
Up to 7kW 30.4A 10A + 30%(20.4) + 5A = 21.1A 6mm² 32A
8kW 34.8A 10A + 30%(24.8) + 5A = 22.4A 6mm² 32A
10kW 43.5A 10A + 30%(33.5) + 5A = 25.0A 6mm² 32A
12kW 52.2A 10A + 30%(42.2) + 5A = 27.7A 6mm² 32A
14kW 60.9A 10A + 30%(50.9) + 5A = 30.3A 10mm² 40A
18kW 78.3A 10A + 30%(68.3) + 5A = 35.5A 10mm² 40A
24kW (large range) 104.3A 10A + 30%(94.3) + 5A = 43.3A 16mm² 45A

Note: Calculated demand values are typical. Always recalculate for specific installation conditions (cable route, installation method, ambient temperature).

Detailed Guidance

Sizing the Circuit

The demand calculation per BS 7671 Appendix 15 uses a diversity factor to account for the fact that not all burners, grills, and ovens operate at full load simultaneously. This is why a 14kW cooker (which would theoretically need a 61A supply) can be served by a 40A circuit.

Step 1: Read the total rated input (kW or kVA) from the cooker's data plate. Convert to amps: I = P/230.

Step 2: Apply the formula: first 10A of rated current + 30% of the remainder + 5A if the control unit has a socket.

Step 3: Select cable from BS 7671 Table 4D5 (flat twin and earth, clipped direct or in insulated wall) at the calculated demand. Apply any derating factors (thermal insulation, grouping, ambient temperature).

Step 4: Select MCB rating — the next standard rating above the calculated demand (16A, 20A, 25A, 32A, 40A, 45A, 50A, 63A).

Step 5: Verify voltage drop: for a single circuit, maximum 5% (11.5V) from origin to terminal. Most domestic cooker circuits are under 15m — voltage drop is rarely an issue.

Cable Routing

Route 10mm² T&E in the most direct path from the consumer unit to the cooker position. Options:

  • Under floor (preferred) — protects cable from mechanical damage, allows easier future replacement
  • Chase in plaster — acceptable if mechanically protected (oval conduit in chase). Vertical chases only — not at 45°
  • In trunking — surface-run trunking at skirting or high-level, appropriate if chasing is not practical

Do not route over the cooker or directly behind it — high temperature zone.

Earth continuity: The circuit earth (CPC — circuit protective conductor) must be continuous and sized correctly. For 10mm² live conductors, the CPC in standard T&E is 6mm² — this is sufficient for a 40A circuit. For 16mm² conductors (very large range cookers), check CPC sizing per BS 7671 Table 54.7.

Cooker Control Unit

Every cooker circuit must have a double-pole isolator (both live and neutral switched) within 2m of the cooking appliance, positioned where it can be operated safely without leaning over the cooker.

Rating: Minimum 45A to BS 4177. Do not use a 13A switched fused connection unit.

Position: Side wall next to the cooker is standard. Do not fit above the hob — grease and heat from the hob will contaminate and damage the unit over time.

Socket outlet: Many control units incorporate a 13A switched socket. Under BS 7671, this socket is permissible if the appliance is not gas. Note: some manufacturers of cooker control units no longer include the socket option due to health and safety concerns (a socket directly next to an electric cooker is a potential hazard if a plug-in appliance is used while cooking). Many electricians now fit a separate socket outlet in the kitchen rather than relying on the control unit socket.

Separate Hob and Oven

Where a separate induction hob (3.5–9kW) and separate electric oven (3–4kW) are installed:

Option 1 — Two circuits: One circuit for hob, one for oven. Each sized and fused independently. Requires two ways in the consumer unit. This is the cleanest solution.

Option 2 — Combined circuit via junction box: One circuit from CU to a junction box, from which two tails run to hob and oven. The circuit must be sized for the combined demand. This is acceptable if both appliances are near each other, but the junction box must be accessible and each branch cable must be correctly sized.

Induction hob note: Some induction hobs specify minimum circuit requirements in their installation instructions (e.g., "dedicated 32A circuit"). Always check the installation manual before designing the circuit.

RCD Protection

Under BS 7671:2018+A2:2022, cooker circuits in domestic premises that are not covered by the main 30mA RCD in a split-load board should have RCD protection. In practice:

  • RCBO on the consumer unit provides both overcurrent and RCD protection for the cooker circuit
  • Split-load board with RCDs covering all circuits: cooker on the RCD side is automatically protected
  • Old-style consumer unit with no RCDs: a 30mA RCCB upstream of the cooker MCB or RCBO provides protection

Frequently Asked Questions

Can I use 6mm² cable for a 15kW range cooker?

Check the demand calculation. 15kW = 65.2A full load. Demand = 10 + 30%(55.2) + 5 = 31.6A. 6mm² cable clipped direct has a current-carrying capacity of approximately 38A (from BS 7671 Table 4D5, method B). So 6mm² is marginally adequate — but only if the cable is not in thermal insulation, grouped with other cables, or in a high ambient temperature environment. In practice, many electricians would use 10mm² cable for a 15kW cooker to provide safe headroom and allow for future appliance upgrades.

Does the cooker circuit need an RCD?

Under BS 7671:2018+A2:2022, all circuits in domestic premises should have 30mA RCD protection. For new cooker circuits, install an RCBO. For existing circuits (not being replaced as part of the job), RCD protection is not retrospectively required unless the circuit is being significantly modified.

My customer wants to move the cooker position. Can I just extend the cable?

Moving the cooker position requires extending the cooker circuit. This means the total cable length from CU increases — you must recalculate voltage drop to ensure it still complies. If the cable is being extended using the same cable size, joining should be done in an accessible junction box, not buried in plaster. The new cooker control unit position must also comply with the 2m rule. This is Part P notifiable work.

Regulations & Standards

  • BS 7671:2018+A2:2022 — IET Wiring Regulations (18th Edition). Appendix 15 covers cooker demand calculation

  • BS 4177 — Cooker control units (switch rating and specification)

  • Approved Document P — Electrical safety in dwellings (notifiable work requirement)

  • BS EN 60898 — MCB specifications (trip characteristics B/C/D for different load types)

  • IET On-Site Guide — Practical supplement to BS 7671 including cooker circuit worked examples

  • NICEIC Technical Guidance — Part P compliance and circuit design guidance

  • Electrical Safety First — Consumer and professional guidance on domestic electrical safety

  • cable sizing — General cable sizing principles and BS 7671 tables

  • consumer units — Consumer unit configuration for new circuits

  • socket circuits — Kitchen socket layout and ring final design

  • kitchen electrics — Full kitchen electrical layout guidance