FER FOCUS: Induction Deduction

What cooks faster and more efficiently than gas, is safer than either gas or infrared electric, keeps your kitchen and serving area cooler and saves you money on make-up air? If you guessed induction cooking technology, you read the headline—and you’re right.

Patents for induction cooking date back to the early 1900s, and the technology was demonstrated at Chicago’s “Century of Progress” Expo in 1933. Manufacturers didn’t produce commercially viable induction equipment until the 1970s. But the high cost and unreliability of early models made induction a non-starter in the U.S. Development of the technology continued in Europe, however, after the Arab oil embargo of the early 1970s raised energy prices. Because of the high cost of energy as well as smaller kitchen sizes, European manufacturers saw a market for equipment that was more efficient, required a smaller footprint and had less of an impact on HVAC. 

Because of its low price and generations of chefs trained to cook with it, natural gas has been an operator’s first choice for years. Conditions today, however, are ripe for growth in induction cooking. TV cooking shows have raised awareness among consumers and professionals, and culinary students are demanding induction cooking equipment and training on how to use it. With rising construction costs, kitchen space is at a premium, and although gas is still cheap, overall energy costs aren’t. 

Manufacturers are responding with a variety of new induction products that provide the technology’s benefits in multiple spots in an operation. In addition to the portable countertop models that operators have used at buffet stations for years, lines include drop-in units for kitchen suites, range tops, wok and stockpot ranges, griddles, hot-food wells, soup warmers and more. Soon you’ll see induction fryers, rice cookers and other equipment. The new generation of products is far more dependable and versatile than past models. 

How Does It Work?

In simple terms, induction cooking or warming equipment uses electricity to create a high-frequency magnetic field. When you put a pan with magnetic properties on the induction coil, the field generates an electric current that runs through the pan. The resistance of the metal in the pan to the magnetic field generates heat.

Instead of waiting for a gas flame or a radiant electric coil to heat, transfer heat to a pan and then transfer the pan’s heat to the food, induction equipment cuts out a step by heating the pan only immediately (the induction top around the pan stays cool), making it much more efficient than traditional electric or natural-gas models. Eliminating that middle step (flame, coil) also means induction cooking is fast. Chef Michel Richard at Villard Michel Richard in The New York Palace Hotel, New York, says the difference in speed needed for gas vs. induction cooking required him to adjust his timing when he first opened the restaurant. 

“You cannot put a pan on the stove and finish chopping your onions,” he says. “The pan gets hot right away. You must have your ingredients ready.” 

Induction also offers precise control. Chef Richard says that kind of precision makes difficult tasks, such as working with sugar or delicate sauces, much easier.

Safety is an additional benefit. Because the pan itself is the heat source, only the area of the induction cook surface directly under the pan gets hot, but even that space cools very quickly the moment the pan is removed. 

Because no open flames are necessary and the majority of the cooktop stays cool, the temperature of the area in which you use induction equipment—whether in the kitchen or display cooking in the front of the house—remains steady. Staff is more comfortable, and there is less of a need for makeup air, reducing the load on HVAC appliances.

Finally, induction is not just an efficient way to heat food: It also saves energy by only cooking when a ferromagnetic pan is placed on its surface. With no pan on top, the surface remains cool and sends no ambient heat into the kitchen space as would a working gas or electric burner.

Now You’re Cooking

Induction “burners,” called hobs, range in both power and coverage area. Depending on the application, manufacturers use one of three types of induction coils (the part of the equipment that generates the magnetic field): round, rectangular and full. 

Round coils typically are the most efficient because they’re designed to deliver power to pans with circular bottoms. Coils may vary in diameter and power for various pieces of equipment. A countertop induction cooktop, for example, may have a 7½-in.-diameter coil with 1,800W of power, plenty for cooking omelettes on a buffet line. An induction stockpot range may have a coil large enough to accommodate a 22-in.-diameter stockpot and provide 8kW of power. 

Rectangular coils give you more flexibility. They deliver power to a larger surface area, so pans don’t have to be placed in a precise spot on the induction surface. Cooks also can use each coil for more than one pan, but the pans will have to share the coil’s available power. In other words, if the coil is rated at 2,500W, it can deliver full power to one pan or half power—about 1,250W each—to two pans. You’ll often find units with rectangular coils spec’d for buffet lines to accommodate a variety of pan sizes and shapes.

So-called “full” coils can be round or rectangular; in essence, they provide edge-to-edge coverage. Putting induction power beneath an entire surface prevents cold spots and offers you the flexibility to place pans wherever you want. Most full-coil induction-cooktop manufacturers incorporate zones into their designs so cooks can saute or fry right next to a zone set at simmer.

Power Up 

The amount of power you need depends on how you intend to use the cooktops. Light-duty units, rated for about 1,800W, can be used for saute stations. Heavy-duty hobs, usually rated for around 2,500-3,000W can be used for frying or boiling pots of water. Hobs ranging from 5-8kW can be used for woks or stockpots. A griddle or plancha may be rated 10kW or more. 

Those of you familiar with gas probably are asking, “What’s that in Btu?” While most of you know that you can convert kWh to Btu/hr.—1 kWh equals 3,413 Btu/hr.—the issue is efficiency; how much of the cooking energy goes into the food?

The U.S. Department of Energy has established some numbers to make your comparison shopping simpler. After a lot of testing, the DOE discovered that natural-gas equipment is approximately 40% efficient while standard induction models are 84% efficient. Using their figures (and we’d better because they’re the folks who determine Energy Star ratings), you can get the equivalent Btu/hr. by multiplying the kWh by 7,185. This equivalency formula is somewhat complicated but factors in the varying efficiencies of gas and induction. 

So, in rough terms, an 1,800W induction hob is the equivalent of a 13,000-Btu gas burner. A 2,500W hob is about the same as an 18,000-Btu burner. A 5kW wok hob is equivalent to a 36,000-Btu burner, and an 8kW stockpot range is similar to a 57,500-Btu burner.

But the comparisons come with caveats. First, the numbers posit a hob that’s working with a good-quality induction-ready pan, i.e., a pan with a high ferromagnetic (iron) content and a base about the same size as the induction coil. Second, because the pan itself transforms energy generated by the induction coil into heat immediately, rather than absorbing heat from another source and then conducting it, induction cooking is fast. The high setting on many induction hobs can burn food quickly if users aren’t careful. 

Take Control 

What most manufacturers do to alleviate or at least ameliorate the latter problem is limit the temperature range in which a hob operates. One manufacturer, for instance, originally provided controls that let cooks adjust the temperature of its countertop hobs from 90˚F-440˚F. Both ends were too extreme, the maker realized, so settings were scaled down to a range of 100˚F-400˚F.

The temperature settings on most models are intended as a guide only. The sensors are located on and note the temperature of the underside of the glass surface on which your pans rest. But the temperature you set won’t tell you the internal temperature of the food you’re cooking, so cooking via temperature is difficult (compared with, say, a combi oven). One maker does offer a temperature probe as an accessory, but you really should consider temperature settings as a guide the way you would terms such as high, medium high, medium, medium low, etc. 

While we’re on the subject, though, models that take the most temperature readings will be the most precise. Microprocessors within the units evaluate temperature readings and adjust power accordingly. One maker claims its multiple sensors evaluate temperature 120 times a second, allowing the unit to adjust power and, therefore, temperature in real time. Look for models with more temperature sensors and/or models that evaluate temperatures faster and more often. Those units likely are better at determining a pan’s size, ferromagnetic quality and position and automatically adjusting their performance to accommodate.

Pay special attention to the equipment’s controls. Some models have simple rotary dials, some have touch-screen LED panels and a few offer both. Most cooks used to cooking on gas prefer rotary dials. Also, touch-screen controls can be difficult to use in the back of the house where hands are likely to be greasy or moist. A number of chefs like having both and being able to use a rotary dial to adjust a hob to a specific temperature indicated on the LED readout. 

Consider, too, how many settings your cooks might need. Most models have around 10—usually two for warming and eight for cooking. Some models offer as many as 20 settings, and one maker offers models with infinitely variable controls, like a gas range. However, if you think about how recipes are written (“simmer on low” or “cook on medium high”), cooks probably don’t need more than about 10.

Final Notes

One of induction cooking’s huge benefits is that the cooktop surface typically is Schott-Ceran glass. While not unbreakable, it is remarkably durable and easy to clean. Because the cooktop stays relatively cool, even spills or boil-overs don’t get baked onto the surface and usually wipe off easily. 

To keep the electronics cool, all cooking hobs have fans like those found in laptop computers. (In fact, if your kitchen temperature exceeds 104˚F with any regularity, you shouldn’t use induction equipment.) The fans need enough clearance to allow proper ventilation. Most units come with removable filters that you should clean at least once a week.

A couple of manufacturers now make drop-in induction equipment for which the electronics can be positioned up to 10 ft. away. That means you can do things like put an induction cooktop on top of a refrigerated base or even a well-insulated oven, giving you even greater flexibility in how you lay out your cooking line. 

Additionally, induction may make big inroads in hot-food-holding equipment. Induction hot-food wells do not require water (you can’t call it a steam table anymore), saving water, energy and the draining of traditional steam tables. Most fit 2- and 4-in.-deep hotel pans. A few manufacturers also have released induction soup kettles (although one maker’s unit still requires a small amount of water). Buffet lines and mobile food carts also benefit from induction equipment.

A last note on power: 1,800W hobs typically operate on standard 115-120V electric service; anything more powerful likely will require 208V or 240V service and a dedicated 30-amp circuit. Factor that into your final choice because bringing in new electrical service can get costly. And while induction equipment is still more costly than natural-gas equipment, the potential savings may provide a quick payback in your operation.