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Cooktops

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Induction, ceramic and gas cooktops.

From our test

Induction, radiant-ceramic or gas?

Which type of cooktop will best suit your needs?

Turn the heat off a radiant-ceramic element that's been on full for a few minutes and it takes some time for the element to cool. Turn off a gas flame and the heat's gone. Professional chefs overwhelmingly use gas for stovetop cooking because it gives them better and more responsive control over the heat. If you're at all adventurous with your cooking, gas is likely to suit you better.

Induction cooktops may offer the best of both worlds: the sleek good looks of ceramic cooktops with the speed and instant control of gas cooking. They heat up incredibly quickly, transferring energy to the cookware faster than any other method of cooking. Induction cooktops are also excellent from a safety perspective: since the element itself does not get hot, it’s safe to touch unless you’ve had a hot pan on it for a while.

With any cooktop, you need to consider installation issues – adequate ventilation and connection to power and fuel supplies. With induction cooktops you also need to invest in new cookware – the cookware used on induction cooktops must be made of ferrous (iron) materials. Pots and pans also need to be within, or close to, the diameter of the elements. Cookware that overhangs won’t heat properly around the edges, and pans that are too small won’t be recognised.

L-R: Radiant-ceramic, induction and gas cooktops.
L-R: Radiant-ceramic, induction and gas cooktops.

How induction cooktops work

Induction cooktops produce a high-frequency magnetic field.
Induction cooktops produce a high-frequency magnetic field.

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.

We knew induction cooking was fast – but to see just how fast, we boiled 1 litre of water on 3 cooktops: induction, radiant-ceramic and gas.

The induction cooktop was at least 3 times faster at boiling water than the radiant-ceramic or gas models.

Approximate time to boil 1 litre of water

  • Induction: 2 minutes
  • Radiant-ceramic: 6 minutes
  • Gas: 8 minutes

Power management

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.

Suitable cookware

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 to 75 percent (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.

Safe with pacemakers?

The area around an induction cooktop is electromagnetically charged. It’s unlikely to affect pacemakers or other implanted electronic devices, but some brands come with a recommendation that you get advice on any possible safety concerns from the manufacturer of your pacemaker or from a doctor.

Induction cooktops - features to look for

If you are buying an induction cooktop, here's what to consider.

  • Safety sensors: 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.
  • Automatic switch-off: If a zone’s not in use, this feature switches it off after a pre-set time.
  • Power boost: A “boost” feature heats food or liquid quickly at the highest setting and then automatically reduces the heat to a pre-selected lower setting.
  • Residual-heat indicator: This is a light that stays on until the temperature gets down to a safe level.
  • Protection against overflows: The hob may shut down with a “beep” if a pan overflows on to the buttons. Remove the overflow, then begin cooking again.
  • Pan detection: 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). See "How induction cooktops work" for more about cookware.
  • Timers: For each cooking zone. Some models have separate timers for general kitchen use.
  • Memory: Allows you to programme the full cooking cycle for a particular preparation.
  • Auto heat-up: 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.
  • Keep warm function: A very low simmer setting that can be used to keep food warm.

Induction cooktops - other considerations

Additional points to think about before buying an induction cooktop.

Installation issues
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).

How cheap to run?
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.

Ceramic cooktops - checklist

If you are thinking about buying a ceramic cooktop, here's what to consider.

  • Durability: The glass used for the cooktop surface is very tough and durable, but it's not unbreakable. If sharp, hard objects are dropped onto it, the glass can be chipped, cracked or broken.
  • Ease of use: The flat surface makes it easy to slide saucepans between elements and on and off the cooktop. But be careful doing this, as you could quite easily scratch the cooktop surface. These scratches won't stop the cooktop working, but they'll spoil its nice smooth "new" appearance.
  • Overall layout: Consider the position and layout of the elements and their size in relation to the pots and pans you usually use. Ideally, a simmer element should be at the front, so you don't have to lean over other elements to stir a sauce. There should also be a large element at the front, for dishes that require high heat and constant attention. Some models also have a dual burner, in which one of the large elements has a small inner ring that can be turned on separately.
  • Controls: Knobs should be easy to grip, touchpads a good size and well separated, with easy to read (and understand) symbols and markings. These factors are especially important for anyone with a disability such as poor grip or eyesight.

    The design of some controls means your hands are very close to the elements when you're adjusting them, which can be dangerous. All knobs and controls should be well sealed, so nearby spills won't leak into the control workings. Touch controls have no gaps that could allow spills to get to the electrics.

    If the controls are close to the front they'll be easy to reach, but if you have young children this may not be a good thing. Controls at the side are safer.

    Make sure the controls have a good range of heat settings. Continuously variable controls are best at getting the heat just right.

  • Residual heat lights: Ceramic tops don't cool quickly, but they do lose colour from the element. Residual heat lights tell you when an element is still hot but not glowing. These lights must be easy to see, even with several pots on the boil.

  • Heat capacity: The elements on an electric cooktop should range from around 1.2 to around 2.2 kilowatts. We found some very small inner elements (0.75kW) were a little underpowered for rice simmering.

  • Cleaning: Ceramic tops should be cleaned with a glass scraper and a cleaning fluid made especially for the purpose. Most cooktops are supplied with both, and you can buy replacements in supermarkets (the fluid costs about $12 and lasts many months).

    You can use a damp cloth with mild detergent for a preliminary clean-up, but avoid harsh, abrasive cleaners and scourers – they will scratch the surface.

  • Dealing with spills: Manufacturers recommend you wipe up sugary spills immediately, because they can pit the surface if you leave them. Of course, you have to be careful if you're cleaning a hot plate.

    Note that because there is often no lip to the top, spills can easily find their way over the side.

  • Cookware: Ceramic cooktops can quite easily become permanently damaged. Use heavy-based, flat, smooth-bottom pans that conform to the diameter of the cooking area. The best choice is probably a stainless steel sandwich base, or enamelled cast-iron.

    Some manufacturers warn that aluminium and copper-based cookware can leave metallic stains on the cooktop. To prevent these building up, you should clean the cooktop regularly – if the metallic stains get burned on to the cooktop’s surface, they may react with the glass and no longer be removable (but they won’t affect the cooktop’s performance).

Gas cooktops - checklist

If you're thinking about buying a gas cooktop, here's what to consider.

  • Flame-failure protection: We think flame-failure protection is essential. If the flame goes out on a gas appliance the gas could continue to flow – and fill the room. Flame-failure protection will either shut the gas off or automatically reignite the flame. We think it should be standard on all gas cooktops … and we don’t recommend models that don’t have it.

    Flame-failure protection comes in 2 forms. The standard version has 2 small rods sticking up next to the burner. 1 is for the ignition (all ignition systems are electric) and the other detects the flame. In models that use automatic re-ignition both functions are integrated into 1 device, so there's only 1 rod next to the burner. To make sure a cooktop has flame-failure protection, check its manual – and do this before you buy.

  • Size and shape: Most gas models come with 4 burners, 1 of which may be a wok burner, which should be sited at the front for safe stirring. Some have 4 or 5 regular burners and an oblong (or fish) burner in the middle that's designed for large rectangular pans, a deep-fat fryer or grill.

  • Burners: Those with an aluminium or enamel surround that sticks out from the base can be difficult to clean as food tends to stick. Some models have burner caps that overlap this surround so they're easier to clean.

    Gas burners are rated for the megajoules per hour (MJ/h) they use on maximum heat. Regular burners should have a good range of heat ratings, from low (around 3.5 to 5MJ/h) to high (up to 10 or 11). Wok burners use around 12 to 15.

  • Controls: Look for good-size knobs with a crossbar grip and an obvious pointer, that click positively into place. If the knobs have to be pushed down before being turned, you'll be less likely to knock them while cleaning and small children will find them harder to switch on.

    They should be easy to understand with simple symbols and markings. Etched labelling is best, as paint can get scrubbed off over time. Run your finger over the labels. Painted ones feel slightly raised, while the etched ones feel flat.

    In most modern hobs, you turn the elements from off through high to low. You can't turn the element off by continuing through low to off. This makes it safe to turn the element right down low, without risking the flame going out while the gas is still on.

  • Ignition There are 3 main ways you can light a gas cooktop:

    • Manual: you use matches or a hand-held sparker.
    • Piezo: turning the knob creates a spark that ignites the gas.
    • Electronic ignition: you'll need to connect the cooktop to a mains power supply, but if there's a power cut you can still use matches.
  • Trivets: These are the frames on which you put the pots. They should be flat and stable on the hob. Those with non-slip feet are less likely to move about and won't scratch the hob surface. Check how much they move up and down and side to side – cast iron trivets tend to be heavier, sturdier and more stable than enamel ones.

    If the trivets are close together you can slide pans around the cooktop without lifting them.

  • Cleaning: A good cooktop should contain any moderate spillage. Look for rounded depressions around burners, sunken hobs and/or partitioning ridges that minimise the spread of mess. Surfaces should be easy to wipe clean. Watch for joins and gaps – they're dirt traps.

    Pan supports and trivets should be easy to remove and wash. Burner collars, knobs and burners should be easy to clean beneath.

  • Safety concerns: If a gas appliance is not burning properly it can produce carbon monoxide, a gas that can cause headaches and nausea, and possibly lead to unconsciousness or even death. It's important to ensure your cooktop is operating safely. Always make sure there is adequate ventilation.

    If an appliance or connector leaks gas you could cause an explosion by lighting a match or even switching on an electrical appliance nearby.

    There are Gas Regulations that cover the safe installation and use of gas appliances, and manufacturers and importers will be required to make a Mandatory Supplier Declaration that their appliances comply with the regulations. The declaration is on the Energy Safety Service (ESS) website. The ESS audits declarations, and consumers can check the declarations for their appliances.

How we test

The same test method was used for all 3 types of cooktop. In addition, ceramic cooktops were tested for chocolate-melting.

First we make white sauce on the simmer-burner or element with the lowest setting. This tests the cooktop’s ability to perform at a low temperature for a long time.

Next we cook rice on the medium-sized burner or element. This tests the "turn down" capacity of the hob and whether the cooktop can maintain a suitable heat at the lowest temperature setting.

We then use a beef and vegetable stir-fry to see whether the cooktop can deliver continuous high heat.

We also assessed the ease of use and cleaning of each cooktop.

Reliability

3214 members told us about their cooktop's reliability in our 2011 appliance reliability survey.

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