Selecting the appropriate cable size for an induction hob installation is a critical decision that directly impacts both safety and performance. With induction cooking technology becoming increasingly popular in UK kitchens, understanding the electrical requirements has never been more important. Unlike traditional gas hobs or even older electric cooktops, induction hobs demand substantial electrical power to generate the electromagnetic fields that heat cookware efficiently. Getting the cable sizing wrong can lead to voltage drop issues, overheating cables, nuisance tripping, or even serious fire hazards.
The complexity of this calculation often catches homeowners and even some electricians off guard. You cannot simply assume that a standard 6mm² cable will suffice for every induction hob installation. The actual requirements depend on multiple factors including the hob’s power rating, the installation method, cable route length, ambient temperature, and applicable diversity factors outlined in BS 7671 wiring regulations. This comprehensive examination explores the technical considerations that determine proper cable sizing for induction hob installations.
Understanding electrical load requirements for induction hobs
Before you can select an appropriate cable, you must first understand the electrical load characteristics of induction hobs. These appliances represent one of the highest power demands in modern domestic installations, frequently exceeding the consumption of electric ovens, immersion heaters, and other fixed appliances. The nameplate rating on your chosen induction hob provides the starting point for all cable sizing calculations, but interpreting this information correctly requires understanding how induction technology operates.
Power rating specifications: 3kw to 7.4kw induction hob models
Induction hobs are manufactured across a wide power spectrum to suit different cooking requirements and electrical infrastructure capabilities. Entry-level models with two cooking zones typically operate at around 3kW to 3.6kW, drawing approximately 13-16 amperes at 230V. These compact units often appeal to apartment dwellers or those with limited electrical capacity. Mid-range four-zone hobs commonly feature power ratings between 6kW and 7.4kW, representing the most popular category for standard family kitchens. At the upper end of the residential market, professional-grade induction hobs can demand 10kW to 11kW, though these higher-powered models remain relatively uncommon in typical domestic settings.
The manufacturer’s specified power rating represents the maximum theoretical load when all cooking zones operate simultaneously at full power. In practice, you would rarely operate every zone at maximum capacity for extended periods. However, electrical installations must be designed to accommodate this maximum demand scenario to ensure safe operation under all circumstances. When reviewing product specifications, ensure you identify the total connected load rather than individual zone ratings, as this figure determines your cable requirements.
Calculating total amperage draw from individual cooking zones
Understanding how individual cooking zones contribute to the total electrical demand helps clarify why cable sizing cannot be based on simple assumptions. A typical 7.4kW four-zone induction hob might feature zone configurations such as a 1.4kW zone, two 1.8kW zones, and a 2.4kW boost zone. The cumulative maximum current calculation uses the formula I = P ÷ V, where power is divided by voltage. For a 7.4kW hob at 230V, this yields approximately 32.2 amperes (7400W ÷ 230V = 32.17A).
However, induction hobs incorporate sophisticated power management systems that prevent all zones from operating at absolute maximum simultaneously. Many manufacturers implement internal load-balancing circuits that automatically reduce power to some zones when others demand maximum output. This technical limitation exists because the hob’s internal components cannot sustain the heat generation from true simultaneous full-power operation across all zones. Despite this built-in limitation, BS 7671 regulations require installations to be designed for the nameplate rating unless specific manufacturer documentation confirms reduced maximum demand.
Single-phase vs Three-Phase power supply configurations
Virtually all domestic induction hobs in the UK operate on single-phase 230V supplies, drawing power through a live, neutral, and earth conductor arrangement. This configuration suits the standard electrical infrastructure found in residential properties. However, some commercial-grade induction equipment and certain high-performance residential models offer
multiple supply options, including three-phase 400V connections. In continental Europe, it is common to see induction hobs with terminals that allow them to be wired either for single-phase or three-phase operation, with power shared across phases to reduce current on each conductor.
In a typical UK domestic setting with a single-phase supply, all of the hob’s load is carried on one 230V circuit. This is why cable size selection and protective device coordination are so important for induction hob installations. Where three-phase is available (usually in commercial kitchens or large properties), the total power can be split between phases, significantly reducing the current per phase and allowing smaller conductors for the same total load. However, three-phase induction hob connections must be installed strictly in line with the manufacturer’s wiring diagram and BS 7671 requirements.
It is worth noting that even where the induction hob offers three-phase terminals, many UK homes do not have a three-phase supply. You should never assume that a property has three-phase availability based on the hob documentation alone. Instead, an electrician will confirm the incoming supply characteristics, maximum demand, and suitability of the existing consumer unit before deciding how best to connect a high-powered induction hob.
Diversity factor application in BS 7671 wiring regulations
One of the most misunderstood concepts in induction hob cable sizing is the application of diversity. Diversity recognises that fixed cooking appliances are unlikely to run at full power on all elements simultaneously and continuously. BS 7671 and the IET On-Site Guide provide diversity guidelines for cooker circuits, which can be applied to most domestic induction hobs. In simple terms, diversity allows the design current used for cable calculations to be lower than the absolute nameplate rating, within defined limits.
For a typical domestic cooker (including an induction hob or combined hob and oven), the commonly used diversity formula is to take the first 10A of the appliance’s rated current, then add 30% of the remainder, and optionally add 5A if a socket outlet is incorporated in the cooker control unit. For example, a 7.4kW hob at 230V has a rated current of around 32A. Applying diversity gives 10A + 30% of 22A (which is 6.6A), resulting in a design current of approximately 16.6A, rounded up in practice. This significantly reduces the calculated continuous load.
So why can’t you always simply downsize the cable based on this lower figure? The key is that diversity is a design tool, not a shortcut to ignore safe current-carrying capacities. Cable selection must still consider installation method, ambient temperature, grouping, and voltage drop. In addition, diversity assumptions are only valid where the hob is used in a normal domestic manner. If the installation is in a semi-commercial environment, or where heavy continuous cooking is expected, a more conservative approach may be necessary, designing closer to the full rated load.
Cable sizing calculations using BS 7671:2018+A2:2022 standards
Once you understand the induction hob’s electrical load and how diversity may apply, the next step is to size the cable using the methodology in BS 7671:2018+A2:2022. Rather than guessing whether 6mm² or 10mm² twin and earth will be “about right”, you work systematically through current-carrying capacities, installation methods, correction factors, and voltage drop. Think of this as following a recipe: miss one ingredient and the final dish—your induction hob circuit—may not turn out safely.
At a high level, the process involves determining the design current (Ib), selecting a protective device with rated current (In) that is equal to or greater than Ib, and choosing a cable with current-carrying capacity (Iz) that is at least equal to In after all correction factors are applied. You must also check that voltage drop and disconnection times remain within the limits set by the Wiring Regulations. In many cases, this confirms that a standard 6mm² cooker circuit is sufficient for a mid-range induction hob, but there are important exceptions.
Determining current-carrying capacity for induction appliances
The first formal step in BS 7671 cable sizing is identifying the design current Ib. For an induction hob, this is derived from the total power rating, adjusted for diversity where appropriate and justified. For example, a 10.8kW hob at 230V has a nameplate current of roughly 47A. Applying cooker diversity might reduce the design current to around the mid-20A range, depending on usage assumptions. This value guides the selection of the protective device and cable.
Once Ib is known, you select a protective device with In ≥ Ib. Common domestic cooker circuit ratings are 32A, 40A, or occasionally 50A, typically using B-type MCBs or RCBOs. The chosen cable must then have a tabulated current-carrying capacity It (before derating) at least equal to In, and a corrected capacity Iz after applying any relevant correction factors. For twin and earth cable in the UK, designers frequently refer to tables based on BS 6004 and BS 7671 Appendix 4.
For instance, 6mm² twin and earth cable clipped direct on a wall (installation method C) may have a tabulated capacity in the region of 47A, whereas the same cable buried in insulation can be significantly derated. In contrast, 10mm² twin and earth might offer tabulated capacities around 64A when clipped direct. The art of good design is matching these capacities to the real installation conditions, rather than relying on “rule of thumb” alone.
Installation method classification: clipped direct, conduit and trunking
The way the induction hob cable is installed has a major impact on its current-carrying capacity. BS 7671 classifies installation methods (such as clipped direct, run in conduit, or buried in thermal insulation), and each method has different base ratings. A cable clipped direct to a surface, with plenty of air around it, can carry more current safely than the same cable tightly packed in insulation or grouped with many others in a trunking system.
Common installation methods for cooker circuits include: clipped direct along joists or walls; run in plastic conduit through voids; or concealed in walls with segments passing through thermal insulation. Each of these scenarios corresponds to a different reference method in BS 7671 Appendix 4. As a result, you might find that a 6mm² cable is perfectly adequate when clipped direct for a short run, but marginal if most of its length is buried in insulation above a kitchen ceiling.
When planning your induction hob installation, it helps to map the cable route in advance. Will you be passing through loft insulation, drilling through solid masonry, or sharing a trunking with other circuits? Each of these choices affects the installation method classification and may require you to uprate the cable size. Ignoring this stage is a bit like choosing tyres for a car without knowing whether you’ll drive only on smooth tarmac or over rough gravel tracks.
Ambient temperature correction factors and cable derating
Another critical consideration for induction hob cable sizing is ambient temperature. Cables are rated at a reference temperature (typically 30°C for PVC insulated twin and earth), but real environments are often hotter, especially in kitchens, loft spaces, and behind built-in appliances. Higher temperatures reduce a cable’s ability to dissipate heat, so you must apply correction factors that effectively “derate” the cable’s current-carrying capacity.
BS 7671 provides tables of temperature correction factors. For example, if a cable runs through a loft that can reach 40°C in summer, a derating factor of around 0.87 may apply. This means a cable with a tabulated capacity of 47A effectively becomes capable of only about 41A under those conditions. If your induction hob circuit is already designed close to the limit, this derating could push the design outside safe parameters, forcing an increase in cable size to restore margin.
Grouping factors can have a similar effect. Where several circuits run together in a trunking or in the same insulation, heat builds up more quickly, and each cable’s current-carrying capacity must be reduced. For a busy consumer unit feeding a new induction hob, oven, and other kitchen loads, an electrician will often consider grouping correction factors as well as ambient temperature. You can think of this in terms of people in a crowded lift: the more people inside, the warmer it gets, and the less tolerable extra weight or heat becomes.
Voltage drop limitations: maximum 3% for fixed appliances
BS 7671 does not only limit cable current; it also limits voltage drop along the length of the circuit. Excessive voltage drop can affect the performance of sensitive electronic equipment, including the power electronics inside an induction hob. For most fixed domestic appliances, the Wiring Regulations recommend a maximum voltage drop of 3% of the nominal supply (around 6.9V on a 230V system) from the origin of the installation to the point of use.
Voltage drop is proportional to both the current drawn and the length of the cable run. This means a high-powered induction hob at the far end of a long cable run is more likely to experience excessive voltage drop than a modest hob located near the consumer unit. Cable cross-sectional area also plays a major role: larger cables have lower resistance and therefore less voltage drop per ampere per metre.
In practical terms, many domestic induction hob installations are well within the 3% voltage drop limit, particularly when the consumer unit is close to the kitchen and the cable run is under 20 metres. However, in larger properties or complex routes, voltage drop calculations can push the design towards 10mm² rather than 6mm² cable to keep the hob performing correctly. A simple rule of thumb is that the higher the hob wattage and the longer the route, the more seriously you must take voltage drop into account.
Cable cross-sectional area selection for common induction hob wattages
With the key principles of electrical load, diversity, and cable derating in mind, we can look at how they apply to real-world induction hob ratings. Most UK domestic induction hobs fall into one of three broad categories: compact 3–4.6kW units, standard 6–7.4kW models, and high-performance 10–11kW appliances. Each category tends to align with a typical cable size and protective device arrangement, though the exact choice always depends on installation details and manufacturer instructions.
It is important to stress that the following examples are indicative rather than prescriptive. Two 7.4kW hobs in different kitchens may legitimately end up on different cable sizes if one is installed via a short clipped-direct run and the other via a long route buried in insulation. Nonetheless, understanding these common configurations gives you a useful benchmark when discussing options with your electrician or planning a kitchen refurbishment.
6mm² twin and earth cable for 7.4kw single-zone hobs
For the typical four-zone induction hob rated around 7.2–7.4kW at 230V, a 32A circuit in 6mm² twin and earth cable is often the standard solution in UK homes. As we saw earlier, the nameplate current at full load is approximately 32A, matching neatly with a 32A MCB or RCBO. When diversity and realistic usage are taken into account, the design current is usually somewhat lower, giving an additional safety margin.
In many cases, 6mm² twin and earth cable installed via method C (clipped direct) or similar will have a tabulated current-carrying capacity greater than 40A, even after moderate derating. This is sufficient to protect the cable under a 32A protective device for a typical residential induction hob. For cable runs up to around 15–20 metres, voltage drop is usually well within the 3% limit, ensuring stable hob performance without dimming lights or stressing the electronics.
Where might 6mm² become marginal for a 7.4kW hob? Situations include long cable runs approaching 30 metres, extensive sections buried in insulation, or significant grouping with other circuits. In such scenarios, voltage drop and thermal derating can push the design closer to the edge, and some electricians will opt for 10mm² cable for additional headroom and future-proofing. However, for the majority of standard kitchen layouts, a correctly installed 6mm² cooker circuit remains entirely compliant and safe for a mid-range induction hob.
10mm² cable requirements for high-performance 11kw models
High-performance induction hobs in the 10–11kW range present a different challenge. At 230V, a 10.8kW hob has a theoretical current of around 47A, which is well above the usual 32A cooker circuit rating. While cooker diversity may still apply, the sheer magnitude of the connected load often leads designers to use 40A or 45A protective devices and, in many cases, 10mm² cable to maintain safe current-carrying capacity and acceptable voltage drop.
On a short, well-ventilated run with favourable installation conditions, a 6mm² cable might technically appear to satisfy current-carrying and voltage drop requirements under diversity assumptions. However, this leaves little margin for future changes, harsh ambient conditions, or misinterpretation of diversity where cooking demand is heavy and frequent. As a result, many electricians consider 10mm² twin and earth the more robust choice for high-powered induction hobs, especially where the manufacturer lists a connection rating of 11kW or provides minimum cable size guidance aligning with larger conductors.
It is also worth noting that some 11kW induction hobs are designed for dual or three-phase supplies in other markets, then adapted for single-phase use in the UK. When the full rating is pushed through a single-phase supply, currents can become significant, and careful attention to derating, protective coordination, and disconnection times is essential. In these higher-load scenarios, upsizing to 10mm² can be viewed as a modest extra cost for a substantial increase in safety margin and future flexibility, particularly if you may upgrade other kitchen appliances later.
4mm² cable applications for compact 4.6kw induction units
At the lower end of the power scale, compact two-zone induction hobs in the 3–4.6kW range can often be accommodated on 4mm² twin and earth cable, depending on the installation. A 4.6kW hob at 230V draws around 20A at full load, which fits comfortably on a 20A or 25A protective device. With cooker diversity applied, the effective design current may drop below 16A, opening the door to 4mm² cables with good capacity and low voltage drop for modest run lengths.
This configuration is particularly common in smaller flats, studio apartments, and annex kitchens where space and electrical capacity may be limited. In some cases, manufacturers offer “plug and play” 13A induction hobs that connect via a standard socket, effectively limiting the maximum usable power to fit within a 3kW envelope. Where a higher-powered compact hob is hard-wired, 4mm² cable offers a balance between ease of routing and sufficient electrical performance, especially when runs are short and installation methods are favourable.
As always, the decision between 2.5mm², 4mm², or 6mm² conductors should be based on formal calculations rather than habit alone. If the cable route involves hot loft spaces, heavy insulation, or sharing containment with other circuits, you may need to step up from 4mm² to 6mm² to maintain compliance with BS 7671. An experienced electrician will consider these factors, as well as the potential for future appliance upgrades, when advising on the most appropriate cable size for a compact induction hob.
Protective device coordination and cable protection
Choosing the right cable size for an induction hob is only half of the story; the other half is selecting and coordinating the protective devices that keep the circuit safe. In a typical UK domestic installation, this means choosing an appropriate MCB or RCBO within the consumer unit, making sure it protects both the cable and the appliance. Proper coordination ensures that if a fault occurs, the protective device will disconnect the supply quickly enough to prevent overheating or electric shock.
BS 7671 sets clear rules for matching protective device ratings to cable capacities. The basic principle is that the protective device’s rated current (In) should not exceed the cable’s corrected current-carrying capacity (Iz). For a 6mm² cooker circuit on a 32A MCB, for example, the cable must be capable of safely carrying at least 32A when all relevant derating factors are applied. If the cable is heavily derated by insulation or grouping, and Iz falls below 32A, then either the cable must be upsized or the protective device rating reduced.
For induction hob circuits, B-type MCBs or RCBOs are commonly used due to their predictable thermal and magnetic trip characteristics. Many hobs feature inrush currents or boost functions, but these are usually well within the tolerances of standard B-curve devices. The advantage of RCBOs is that they combine overcurrent and residual current protection in a single unit, helping meet RCD requirements for circuits supplying equipment in domestic premises, including kitchens. Ensuring correct disconnection times under earth fault conditions is critical, particularly where metal kitchen worktops, sinks, and pipework may be present.
In some installations, an isolator switch with an integral 13A socket is fitted near the hob. In such cases, the cooker circuit diversity formula may allow an additional 5A to be considered, and the protective device selection must take into account both the hob load and any accessories that may be plugged in. The overall objective is clear: the protective device must trip fast enough under fault conditions to protect people and property, yet allow normal induction hob operation without nuisance tripping during everyday cooking.
Cable installation routes and mechanical protection requirements
Beyond electrical capacity, the physical route and protection of the induction hob cable are vital elements of a safe installation. Cables running through walls, floors, and ceilings must be protected against both mechanical damage and the risk of hidden contact with drilling, nailing, or fixing operations in the future. BS 7671 provides detailed rules for permitted cable routes, safe zones, and the use of mechanical protection or RCDs for concealed wiring.
In domestic kitchens, cooker circuits often run from the consumer unit through floor or ceiling voids and down the wall behind the hob location to a cooker control unit. Where cables are concealed in walls at a depth of less than 50mm, they must either be run in prescribed safe zones (such as directly above or below accessories) or provided with additional mechanical protection. Where such protection is not practical, RCD protection becomes mandatory, which is one reason why many modern induction hob circuits are fed via RCBOs.
When planning the route, electricians also consider practical installation aspects: avoiding excessive bends, minimising runs through thermal insulation, and steering clear of sources of heat that could raise the cable temperature. Mechanical protection might take the form of steel conduit, capping, or trunking in vulnerable areas such as garages, service cupboards, or exposed walls. Although 10mm² cable can be stiffer and harder to route than 6mm², good planning of the route and appropriate back box depths at the cooker switch can mitigate installation difficulties.
From a homeowner’s perspective, understanding the importance of cable routing and protection helps explain why installing or upgrading an induction hob circuit is rarely as simple as “just pulling a new cable”. Each route choice has implications not only for safe zones and RCD requirements but also for thermal performance and future flexibility. Asking your electrician how they plan to route and protect the cable is a useful way to gauge whether the installation is being designed with long-term safety and compliance in mind.
Manufacturer-specific cable recommendations: bosch, siemens and AEG compliance
Finally, even the most carefully calculated cable size must be cross-checked against the induction hob manufacturer’s own installation instructions. Brands such as Bosch, Siemens, and AEG publish detailed connection requirements that may include minimum cable sizes, maximum protective device ratings, and specific wiring diagrams for different supply configurations. These instructions are not optional; BS 7671 requires that fixed appliances be installed in accordance with the manufacturer’s recommendations.
For many mid-range Bosch and Siemens hobs in the 6–7.4kW category, the manufacturer may state that a 32A supply with a minimum 6mm² cable is required for single-phase connection. Higher-powered models around 10–11kW may specify 10mm² cable and a 40A or 45A supply when used on a single phase, or provide alternative three-phase wiring options for markets where that supply is standard. AEG and other premium manufacturers often include similar guidance, sometimes explicitly warning against under-sized cables that could overheat during prolonged high-power operation.
Where the manufacturer’s guidance appears more conservative than your own BS 7671-based calculations, the safer course is to follow the appliance documentation. For example, even if diversity and installation conditions indicate that 6mm² might cope with a certain hob model, a clear instruction from Bosch or AEG to use 10mm² should override that judgement. Not only does this align with best practice, but it also protects the manufacturer’s warranty and reduces the risk of disputes if a problem arises later.
In summary, cable sizing for induction hobs is a collaborative process between the Wiring Regulations and the manufacturer’s requirements. BS 7671 provides the framework for safe electrical design, while brands like Bosch, Siemens, and AEG supply appliance-specific details that refine that design. By respecting both, you ensure that your induction hob is not only efficient and responsive, but also safely supplied by a correctly sized and properly protected cable for many years of reliable cooking.