Cooking with magnetic fields? Meet induction cooktops

Humans first began cooking when they discovered how to create fire. Since then, cooking has been a key part of human health and culture. We’ve developed new and better ways to generate heat for cooking, from coal ovens to gas burners, to electric stovetops. These involve generating heat, then applying it to the cookware containing food, or the food directly to heat it – a process called thermal ‘conduction’.

Microwaves introduced electromagnetic radiation to cooking, meaning for the first time heat could be produced within the food itself rather than applied externally. But microwaves ovens are limited – they generally can’t brown, saute, or fry.

The latest development in cooking technology is called ‘induction heating’. It can be more efficient, faster, and safer than thermal conduction, while more versatile than microwave cooking. Could an induction cooktop be your next kitchen upgrade? Read on to find out.

induction cooktop guideWhat are induction cooktops?

Induction cooktops are a relatively new type of cooking technology that uses magnetic fields to induce heat within cookware placed on the cooktop. They’ve only recently begun catching on as a faster, safer, more efficient way to cook. The cooktop surface is a smooth, continuous sheet of glass or ceramic, with tightly wound coils underneath which produce electromagnetic fields just underneath this surface. The location of the coils, referred to as ‘cooking areas’ are marked on the surface except where the entire surface is a ‘cooking area’.

How do induction cooktops work?

Induction cooking works by using magnetic induction, instead of thermal conduction from a flame or electrical heating element. As magnetic induction directly heats the pot or pan, rather than generating heat which then transfers to the pot, it can heat up very quickly and efficiently.

Induction cooktops have a coil or coils of copper wire underneath the surface. When turned on, an alternating current passes through the coil to produce an alternating magnetic field, which in turn creates a magnetic flux. This changing magnetic field repeatedly magnetises the pot or pan, creating eddy currents (smaller electric currents) which, due to the resistance of the pot, produce heat.

In other words, induction cooktops use rapidly changing magnetic fields to create heat from electrical resistance in the pot itself. It sounds complicated, but it’s just using the basic properties of electrical currents to produce targeted heat.

Note that this only works on cookware that is made of a ‘ferrous’ material, which means it has a high iron content. You can check whether your cookware will work by seeing if a magnet sticks well to the base. Cast iron, aluminium with a stainless steel bottom, and stainless steel/aluminium layered cookware works well on an induction cooktop. Glass, copper, or pure aluminium cookware won’t work.

induction heat cookingWhat kinds of induction cooktops are there?

Most induction cooktops work the same way. The two major variables are the size and layout of the cooking zones, and the controls. Naturally you’ll need to make sure you choose a size that is compatible with the bench space where you wish to install the cooktop. However, on the cooking surface itself, there is quite a bit of layout variation.

You can choose a number of configurations of traditional circular cooking zones and rectangular continuous cooking zones, depending on the kinds of cooking you usually do. When looking at induction cooktops, visualise what combination of pots and pans you use for cooking, and which layout best suits your cooking habits.

Most induction cooktops feature digital touch controls, which can provide a lot more heat precision control than conventional cooktops. Some also include additional features such as child locks, timers, pause buttons, and automatic switch-offs.

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Are induction cooktops safe?

Induction cooktops are actually much safer than conventional cooktops, because the heat is being produced exclusively within the pan. Once you’ve taken the pan off the cooktop, it cools much faster as any heat left on the cooktop is purely from contact with the hot pan.

It’s also safer if you forget to turn off the stovetop – no heat is produced except when a pot is placed on the cooking area, so while electricity will still be flowing through the cooktop, there won’t be any heat produced to accidentally burn anyone.

How much do induction cooktops cost?

Below is a general range of prices of cooktops currently available from some major brands and retailers. Price varies by model and size, as well as coil quality, so don’t let price be your only guide.

Induction cooktops haven’t quite caught on in terms of popularity yet, but they’re a rapidly growing market so you may expect to see some more budget-friendly options appear in the near future.

Brand Low End High End
Bosch $1,699 $3,999
Blanco $999 $2,499
Electrolux $1,299 $4,269
Fisher & Paykel $999 $3,199
Miele $1,999 $4,999
Samsung $2,299
Smeg $1,890 $3,490
Westinghouse $1,049 $2,769
Chef $828 $1,269
Whirlpool $1,199 $1,699
Ikea $389 $1,399

Source: Respective brand websites November 2016

Below we’ve described three different examples of 60cm cooktops to give you an idea of what kinds of features you can find in induction cooktops. These products were selected randomly from the major brands, and inclusion here does not constitute a recommendation or endorsement over other products.

cooking with magnetic fieldsBlanco Maxisense 3 zone induction cooktop

With individual 10-level temperature settings and 99 minute timer for each of the three cooking areas, the Blanco Maxisense includes a ‘Boost’ function which pushes to maximum power for 5min unless deactivated. When a timer ends, the cooktop will beep and the cooking area will turn itself off, so you won’t accidentally overcook anything.

It also features ‘AcuSense’ technology which Blanco says automatically recognises the size and shapes of pots as well as their position on the cooktop – but doesn’t explain what this offers above the standard function of induction heating.

A number of sensors and automatic functions keep operation safe and efficient. The overflow cut-off function detects if liquids come into contact with the control panel, and automatically switches off the cooktop until dried. The residual heat display for each cooking area lets you know if an area is still hot, and the ‘lock’ function means the cooktop cannot accidentally be turned on by children or while cleaning it. This cooktop retails for around $1,300.

Cooking Zone Regular Power Boost Power Diameter Min. Cookware Diameter
Front left 2300W 3000W 220 mm 100 mm
Back left 1100W 1400W 180 mm 90 mm
Right 2300W 3000W 270 mm 110 mm

induction cooking stovetop by electroluxElectrolux EHI645BB

Each of the four cooking areas on this cooktop has 10 heat settings including a boost function that lasts 10min before automatically turning off (unless manually disabled earlier), and a 99 minute timer with beeper and automatic switch-off upon time elapsing. There is also a three-step residual heat indicator (cooking, keep warm and residual heat) on each zone.

The Stop+Go function sets all cooking zones in operation to the lowest heat setting, which can be used to warm up your cookware or keep your cooked food warm until you’re ready to serve. The automatic heat up setting sets the highest temperature for some time, then decreases to your desired cooking temperature.

There’s also a lock function that prevents accidentally changing the heat setting, which is handy for when you’re cleaning or have little ones around. The cooktop will automatically switch off if:

  • all cooking areas are set to temperature level 0, or
  • there is a spill or object on the control panel that stays there for more than 10 seconds, or
  • the cooktop becomes too hot such as if a pan boils dry, or
  • you use incompatible cookware, or
  • if a zone’s heat setting is not turned off or changed within a certain period of time (after between 1.5 to 6 hours, depending on temperature)

If you need a larger cooking area, the bridge setting allows you to connect the two left-hand side cooking zones to operate as one. Bridged zones cannot use the boost function. This cooktop retails for around $2,400.

Cooking Zone Regular Power Boost Power Diameter Min. Cookware Diameter
Front left
Front right
Back left
Back right
2300W 3200W 210 mm 125 mm

induction cooktop by fisher and paykelFisher & Paykel CI604DTB3

The four cooking areas on this cooktop are, rather than round zones, large rectangular zones called ‘SmartZones’. The two zones on a given side can be bridged to form one larger zone to accommodate larger pots and pans. The whole zone is activated when a pot is detected, so you can have multiple small pots on the zone and they will all be detected as if they were one large pot.

There are ten heat settings, with the highest being the ‘Powerboost’ function which when activated will remain on for 10 minutes, unless deactivated earlier, then switches to setting 9. The Powerboost function is not available on bridged zones. You can use the auto heat-reduce option to set a zone to first heat at the maximum setting, before automatically reducing to your desired cooking temperature. The timer for each zone also includes an option to have the zone automatically turn off once time has elapsed.

Each cooking zone has a residual heat indicator that will flash if the surface is too hot to touch. If no pan is detected on a zone for 10 minutes, the applicable cooking zone/s will turn off. The cooktop will automatically turn off if:

  • you don’t respond to the alert that sounds when a cooking zone is turned on without a compatible pot or pan placed on it, or
  • no heat setting is selected within 20 seconds of being turned on, or
  • there’s a spillage on the control panel

A ‘lock’ function allows you to lock the control panel for safety while you’re cleaning or have children around. This cooktop retails for around $1,950.

Cooking Zone Regular Power Boost Power Diameter Min. Cookware Diameter
Front left
Front right
Back left
Back right
2100W 3700W SmartZone 120 mm (un-bridged)
250 mm
(bridged)

Why should I choose an induction cooktop?

An induction cooktop provides a number of advantages over other types of cooktops. The main difference in quality between different induction cooktops comes down to the induction coils.

  • Rapid heat change is possible, compared to an electric cooktop which requires time to heat up or cool down.
  • As a smooth, continuous surface, it’s very easy to clean as there are no nooks and crannies for food to get stuck in. You can even safely put paper towels underneath the pot while cooking to catch any spills and protect the bottom of your pot from scuff marks.
  • The surface doesn’t get as hot as an electric or gas stove, and even while turned on won’t produce heat except in any pot or pan placed on the surface. This makes it much safer.
  • Heat is produced only where you want it (directly in the pot), which is more efficient than producing heat to then transfer to the pot. This also means less energy is wasted on heating up anything that isn’t the pot, such as your kitchen. While some heat will radiate out of the pot and the food itself, it’s far less than with other types of cooktops, so you’re less likely to find yourself heating up along with your cooking!

The biggest downside to an induction cooktop is that it isn’t compatible with all cookware. If you prefer using glass, copper, or pure aluminium cookware and are unwilling to replace it, an induction cooktop isn’t a great choice for you. On the upside, there’s ongoing research into making induction cooktops that work with any kind of metal.

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