Magnetic cooking: want to boil water in an instant? Have almost instantaneous control over your cooking temperature? An induction cooktop might be for you.(Test: induction cooktops)

They're fast, efficient--and expensive. Induction cooktops have been relatively common overseas for years, but they're only just beginning to make a dent in the market here compared to the more common gas, radiant coil and ceramic options.

We tested four models currently available on the Australian market from AEG, ASKO, BRANDT and MIELE. They'll each set you back around $3000, so they're certainly a lot more expensive than other cooktops. But are they worth the extra cost?

HOW THEY WORK

Although they look fairly similar to a ceramic cooktop, it's the way they work that's unique. Each 'element' (induction coil) on the cooktop generates a magnetic field that induces heat in steel cookware placed on top of it. In essence the saucepan or pot becomes the element, so the cooktop surface doesn't get as hot as other cooktops (see the photo, page 33).

Because most of the heat and energy are produced in the saucepan itself, the heat response is quicker and more efficient. With more conventional electrical cooking, the heat first has to be transferred from the element, through the ceramic and then to the saucepan and its contents.

On top of the cost of an induction cooktop, you may also have to buy a new set of cookware if your current set isn't compatible. The base of the cookware must be made of a ferrous metal (a metal that can be magnetised). Cast iron, steel, some enamelled steel and stainless steel pans with an iron base or core are suitable, but you can't use glass, aluminium, copper or many stainless steel pans. Check the cooktop manufacturer's recommendations for all pans, particularly enamelled steel, as some aren't suitable and may explode. The base of the saucepan should be flat, not distorted or dented, or cooking performance will be affected.

COOKING COMPARISONS

We subjected the induction cooktops to four cooking tests: making white sauce, cooking rice, cooking a stir-fry and melting chocolate. (See Cooking performance score, page 34, for more on these tests.) All four models performed extremely well--better than comparative cooking tests on ceramic and radiant coil cooktops, and generally equal to or better than gas. With instantaneous control over the heat settings, you have greater control over the cooking. See Cooktop type comparisons, right, for comparative scores from tests we've conducted over the last few years.

While the cooking test results for the induction cooktops were exceptional, like any innovation it will take some getting used to, especially when changing from other types of cooktop. The power settings range from very low to very high and change almost instantaneously when you adjust them. Once you're used to the different power settings you should achieve excellent cooking results.

The difference in energy efficiency between the four induction cooktops tested was minimal, as was the difference in boiling time. They're certainly much …