An induction cooktop heats the pan itself using a rapidly changing magnetic field, which is why it is fast, precise and efficient. This guide explains the physics, how it compares with gas and resistive cooking, cookware needs and supply capacity. An induction cooktop heats the pan, not the glass. A copper coil under each cooking zone carries alternating current at a high frequency, creating a rapidly changing magnetic field. When a pan with a magnetic base sits on the zone, that field induces electric currents inside the metal, and the metal's resistance turns those currents into heat. The glass surface only warms because the hot pan sits on it. This direct transfer is why induction responds quickly, controls finely and wastes relatively little energy.
The physics under the glass
Each zone is driven by power electronics. The cooktop first converts mains alternating current to direct current, then switches it back into alternating current at tens of kilohertz, far faster than the 50 Hz mains supply. That high-frequency current flows through the coil and produces the magnetic field.
Two effects then heat a suitable pan:
- Eddy currents. The changing field induces circulating currents in the pan's base. At high frequency these currents crowd into a thin layer near the surface, known as the skin effect, which raises the effective resistance and concentrates heating where the pan meets the food.
- Magnetic hysteresis. In ferromagnetic metals such as iron and many steels, magnetic domains flip back and forth with the field, and a little energy is released as heat each time.
Sensors detect whether a suitable pan is present. Lift the pan away and power stops flowing almost immediately. Temperature sensors under the glass also reduce power if a pan boils dry or overheats, and residual heat indicators show which zones are still hot from contact with a pan.
How efficient is induction?
Efficiency here means the share of energy used by the cooktop that ends up in the pan and food. Typical ranges vary with the test method and the pan, but the pattern is consistent:
| Cooking method | Typical share of energy reaching the pan | Where the rest goes |
|---|---|---|
| Induction | Around 80-90% | Small losses in the electronics, the coil and the glass |
| Resistive (ceramic or coil) | Around 70-75% | Heating the element and glass, which then radiate into the kitchen |
| Gas | Around 30-40% | Hot combustion gases flowing up and around the sides of the pan |
A quick calculation shows the scale. Bringing 2 litres of water from 20°C to boiling takes about 0.19 kWh of heat. At 85% efficiency, an induction zone uses about 0.22 kWh, while a gas burner at 35% needs the energy equivalent of about 0.53 kWh. Beyond the numbers, induction adds less heat to the kitchen on summer evenings, and heat drops quickly when a zone is turned down.
Cookware that works
Induction needs a base that responds to magnetism. The simplest test is a fridge magnet: if it clings firmly to the bottom of the pan, the pan will work.
- Works well: cast iron, enamelled cast iron, carbon steel, and stainless steel pans with a magnetic base layer.
- Does not work on its own: aluminium, copper, glass and ceramic, unless the pan has a bonded magnetic base marked as induction compatible.
- Flat bases matter: a warped base sits unevenly in the field and heats unevenly.
- Size matters: a pan much smaller than the zone may not be detected, and one much larger heats mainly in the centre.
Adaptor plates let non-magnetic pans sit on a steel disc that heats up, but this turns induction back into conduction and gives up much of the efficiency advantage.
What an induction cooktop draws
Power ratings are higher than many people expect. A single zone commonly runs from around 1.4 kW to over 3 kW, and many offer a short boost setting. A typical four-zone cooktop may carry a total rating of about 7 kW or more. In everyday use, however, zones cycle on and off and rarely run flat out together, so the energy used for a meal is usually modest; the boiling example above used less than a quarter of a kWh.
Timing affects what that energy costs. Most households cook in the early evening, when rooftop solar output is falling and time-of-use peak rates often apply, so an induction cooktop usually draws from the grid or a battery rather than directly from the panels. Weekend lunches and slow daytime cooking are the occasions when solar can cover much of the load.
Most cooktops also manage power internally. When two zones on the same side are pushed hard, the electronics share a combined limit between them, and many models can be set by the installer to a lower total current to suit the home's supply. This matters if a home battery is expected to run the cooktop in the evening, because a battery's continuous discharge rating limits how much power it can deliver, as explained in how battery storage technology works.
Supply capacity and wiring
Replacing a gas cooktop is an electrical project, not just an appliance swap. A licensed electrician needs to check:
- The circuit. A full-size induction cooktop usually needs its own dedicated circuit, with cable and protection sized for its rating, commonly around 32 A for single-phase models.
- The switchboard. There must be space and suitable residual current protection for the new circuit.
- Maximum demand. The electrician calculates whether the home's total expected load, including the cooktop, stays within the capacity of the consumer mains and service protection.
- Future loads. If a heat pump, EV charger or air conditioning upgrade is also planned, assessing everything together avoids paying for repeat upgrades.
Disconnecting and capping the gas supply must be done by a licensed gasfitter. Treating the kitchen as one part of a wider electrification plan, alongside solar, storage and EV charging, is discussed in solar, EV and the smart home energy ecosystem.
Next steps
The Induction & Electrification Assessment in the Blue Energy Solar market checks switchboard and supply capacity for an induction cooktop, heat pump and EV charger and suggests a sensible order of upgrades, for $199 with the fee credited if the work proceeds. The price is indicative and confirmed after a site assessment. For solar or a battery sized around an electric kitchen, request a free assessment from Blue Energy Solar.
Frequently asked questions
Is the humming or buzzing from an induction cooktop normal?
Yes, some sound is normal. Pans made from layers of different metals can vibrate slightly at high power settings, producing a hum or buzz that usually quietens when the setting is reduced. A cooling fan also runs to protect the electronics and may continue briefly after cooking ends. Loud clicking, rattling or repeated error codes are different and should be checked by a qualified technician.
Will an induction cooktop work during a blackout?
Not on grid power alone. It will only work if the cooktop circuit is connected to a backup-capable battery system and the inverter's backup power rating can carry the load. Cooktops are often left off essential backup circuits because of their high power draw, so check the backup design if cooking during outages matters to your household.
Can the glass surface scratch or crack?
The glass-ceramic top is tough but not indestructible. Sliding heavy cast iron can scratch it, and dropping a heavy pan on an edge can crack it. Lift rather than drag pans, keep pan bases clean so grit is not ground into the surface, and wipe spills once the glass has cooled. A cracked cooktop should not be used until it has been repaired or replaced.
Please Login or Sign up to be able to comment