Find out how induction cooktops work and what to consider when buying one.
Induction cooktops produce a high-frequency magnetic field. When you put cookware such as a steel-plated pan on to the magnetic field, energy is transferred into the metal.
The pan then heats up and cooks the food directly. And because the heat is generated inside the pan, the cooktop stays reasonably cool.
Induction cooktops are highly responsive – unlike a conventional radiant-ceramic cooktop. When you adjust the temperature, the change happens immediately.
You sometimes hear whistling or cracking sounds (especially if you’re using multi-layered saucepans), humming when you use high power levels and clicking when zones turn “on” or “off” or change their power levels. This is all perfectly normal.
The induction cooktop was at least 3 times faster at boiling water than the radiant-ceramic or gas models.
Before you buy an induction cooktop, think about what size you need and how many cooking zones you’re likely to use at once.
Induction cooktops mainly come in 3 size options – 60cm, 90cm or somewhere in between. They have 3 to 6 cooking zones and some zones can combine into a flexi-zone.
However, if you’re using all the zones at once, the cooking space can become quite cramped and cooking can begin to interfere with the controls, making them greasy and unresponsive to touch.
As a general rule, a 60cm model can accommodate 3 zones comfortably, 70-85cm cooktop 4 zones, and a 90cm model 5 zones.
You should also consider the cooking zone layout. A very good layout has the small and large cooking zones at the front, or all zones are the same size. This means you won’t be leaning across cooking zones when you’re stirring.
The power supply to the cooking zones works in a way that takes some getting used to. The cooking zones are organised into pairs (usually arranged as 1 pair on the left side and 1 pair on the right side).
The maximum available power is shared between the 2 cooking zones in a pair. When the “power boost” function is selected for 1 cooking zone, the additional power is made available by limiting the power of the other cooking zone in the pair. For some cooktops, the power boost function can only be used if the other cooking zone in the same pair is switched off. If you want maximum power in 2 pans, use 1 cooking zone in each pair.
For some induction cooktops, even when not using the “power boost” feature, if all cooking zones are in use at the same time, some cooking zones may be reduced in power. Check when buying whether the cooktop you want has any limitations.
Cookware used on induction cooktops must be made of ferrous (iron) materials. Induction cooktops won’t work unless you use magnetisable cookware.
Cast-iron cookware – including ceramic- or porcelain-coated cast iron – is fine. Some stainless-steel and multi-layered cookware is also suitable. But copper or aluminium pans won’t work unless they’ve got multi-layered bases with an outer layer of suitably ferrous material. Non-stick pans without an outer layer of iron won’t work either.
Most cookware will say whether it’s suitable for induction cooktops.
Tip: Take a magnet with you when shopping for cookware. If the magnet sticks to the base of a pan, the pan will work on an induction cooktop.
For induction cooktops to perform most efficiently, a pan’s base must cover at least 60-75% (depending on the model) of the cooking zone and be no more than the recommended maximum diameter. The cooktop’s manual will tell you the recommended maximum diameters.
The area around an induction cooktop is electromagnetically charged. It’s unlikely to affect pacemakers or other implanted electronic devices, but some pacemaker brands recommend you keep a distance of at least 60cm from an induction cooktop. Before you buy get advice on any possible safety concerns from the manufacturer of your pacemaker and your doctor.
If you are buying an induction cooktop, here’s what to consider.
Flexi-zones (sometimes called a “bridge function”), where both left or both right zones can be joined and operated as a large cooking zone, increase the flexibility of an induction cooktop. When joined, you can use large oval or rectangle pans on the cooktop. It’s important to keep stirring when using bridged zones as there is a cooler spot where the zones meet.
These monitor the temperature of the bottom of the cookware. So if an empty pan’s left sitting on a zone that’s “on”, the sensor adjusts the power output to avoid damaging the cookware or the cooking zone.
If a zone’s not in use, this feature switches it off after a pre-set time.
A “boost” feature heats food or liquid quickly at the highest setting and then automatically reduces the heat to a pre-selected lower setting.
This is a light that stays on until the temperature gets down to a safe level.
The hob may shut down with a “beep” if a pan overflows on to the buttons. Remove the overflow, then begin cooking again.
When you remove a pan from the cooking zone, the zone stops operating – and a display symbol appears, telling you what’s happened (when you put the pan back the symbol disappears and cooking resumes). If you try to use cookware that’s not suitable, yet another display symbol lets you know what you’ve done (and after a short period the zone switches itself off).
For each cooking zone. Some models have separate timers for general kitchen use.
Allows you to programme the full cooking cycle for a particular preparation.
Allows the cooking zone to heat to a higher setting, then automatically turn down to a preset setting after a certain amount of time. This is handy if you’re cooking rice using the absorption method and want to bring it to the boil initially and then simmer.
A very low simmer setting that can be used to keep food warm.
Induction cooktops need to be specially installed. The electronics shouldn’t be exposed to significant amounts of heat during cooking – and so they usually come with fan-cooled “heat sinks” to disperse the heat. (You may hear some noise from the heat-sink fans during and after cooking.)
Adequate ventilation space is also essential. The manufacturer’s installation dimensions must be carefully followed.
Not all induction cooktops can safely be installed above every brand of under-bench oven. Check the installation instructions to see which combinations are acceptable.
Tip: Be aware that manufacturers may try to steer you towards using one of their ovens, even though other brands would work fine.
Because they heat so quickly, these cooktops draw plenty of energy. A normal power socket has a 10-amp connection, but an induction cooktop may require a connection of 20, 32 or even 42 amps. This must be hard-wired by a licensed electrician (the cost will depend on how difficult it is to install a dedicated circuit between the main power board and the kitchen). Before buying an induction cooktop, we recommend getting a quote for installation costs.
The sales talk highlights induction cooktops’ efficiency and cost savings – but when we compared them with a ceramic cooktop they weren’t any cheaper to run over the same period of time.
Because it boils water in seconds, an induction cooktop may save a little energy. But the purchase price is high. And if you don’t have suitable cookware there’s the added expense of new pots and pans.