We don’t often think about the energy we use for cooking. In the most economically disadvantaged countries, gathering energy for cooking is a major component of people’s time (mostly women), and smoke from wood cooking fires is a significant health issue. One great solution for these people is solar cookers, and this organization is my favorite non-profit, because it helps the planet’s poorest people while doing environmental good.
In industrialized countries, cooking energy is off our radar. We first started thinking about it seriously when Jill got the book by Kate Heyhoe called Cooking Green. The authordescribes a lot of simple techniques to reduce cooking energy. Reading this book, though, pushed me to try a technology I’d heard of before but associated with very costly appliances, the induction cooktop.
Gas stoves aren’t very efficient
Gas cooktops place a flame beneath the cooking pot, and heat up the bottom of the pot, which transfers heat to the food within. A conventional gas cooktop is a tad less than 40 percent efficient. You can sense this because you can feel the heated combustion products rising around the pan, and often the handle of a fry pan gets too hot to touch when used on a gas cooktop.
Gas also has the disadvantage of creating these combustion products in your kitchen. Harvard School of Public Health’s venerable Six Cities Study is one of the research efforts that has linked gas cooking with increased respiratory symptoms in children. When I use a gas range or oven I always use the range hood if one is available, to exhaust at least some of these pollutants outdoors.
Nonetheless, gas has always been the preference of the serious cook (and wanna-bes) and certainly in high-end homes there has been a proliferation of commercial-like ranges the size of Mini-Coopers with associated commercial-like range hoods which suck pets and small children right out of the kitchen. Gas cooktops are preferred over electric cooktops because they can be turned down quickly.
Traditional electric cooktops are more efficient than gas — about 70 percent — but the thermal mass in the burner has made them slower to respond than their combusting competition. There are more modern electric burners like halogen cooktops that are speedier, yet, like the gas cooktops, they heat the pot which then heats food.
An oscillating magnetic field
Induction cooktops work by inducing a current in the piece of cookware with an oscillating magnetic field. The resistance to this current flow creates heat. The energy is delivered directly in the pot without first heating it from the outside, so it is both fast and efficient — efficiency in the mid-eighties is often cited. Using an induction cooktop limits your choice of cookware, because it has to be ferrous: iron, steel, or some kinds of stainless steel.
We got interested in trying an induction cooktop and learned that single-burner units were available on eBay for under $100. We bought one sold by Burton that was rated at 1,800 watts, about as large as is possible to use on a 120-volt circuit.
We began to experience the benefits although there were drawbacks, too — this particular unit has a cooling fan and is a bit noisy. It was, however, almost instantaneous in its turn-down of temperature — you could have a rolling boil and hit the controls and bingo — it was simmering or less. And if water boiled over onto the cooking surface, it didn’t even sizzle, because the heat is generated in the pot, not the cooker.
It was time to get rid of the old gas range
When we moved to our current home, we inherited a KitchenAid gas range. I thought it was surprisingly slow to bring large pots to a boil, and I disliked having to use the noisy range hood every time I was cooking.
We began to look for electric ranges with induction burners. One of the least costly was this Frigidaire that had the intriguing (and money-saving) feature of having two induction burners and two conventional electric burners, all beneath the same glass top. You can keep all your cookware because the non-ferrous stuff is usable on the conventional burners. We ordered one.
The large induction burner is over 3,000 watts and is the fastest burner I’ve ever used. I cooked eleven pounds of potato salad in two pots a few weeks ago, putting the larger pot on the induction burner and the smaller one on the conventional burner. The spuds on the induction burner were done before the other pot came to a boil.
When you get a higher-end appliance like this one, you get the good with the bad. It’s all digital push pad rather than nice analog twisty dials — I hope the digital brain lasts a long time.
On the other hand, it has convection oven modes, and lots of cool racks. The conventional burner side has the nifty feature of a “bridge” burner between the two round burners, which can be used to apply even heat to a griddle that straddles the whole side of the cooktop. Great for pancakes and French toast.
Our new stove uses a fraction of the energy of the old one
I have a pretty good idea of how much energy we used in the gas range, because for several months our only gas appliance was the range. From a delivery on September 27, 2010 until we installed the new electric range in early April 2011, we used about 13 gallons of propane, or 2.1 gallons/month. That’s a gross input of about 192,000 BTU/month.
I have a kWh meter on the electric range, and in four months it’s consumed 51 kWh, which works out to 174,000 BTU in total, or about 44,000 BTU/month. That’s twenty three percent of the gas range consumption. If primary energy is accounted for, the new range is using about 60% of the primary energy that the gas range did.
In addition, the lack of combustion means that we only use the range hood when we have odors or excess moisture — not as a matter of course. This will save heating energy in the colder seasons.
Overall, we think the induction range is the bee’s knees. South Mountain Company has put a couple of them into custom homes, and the owners love them, both for their cooking speed and controllable output, and for the health benefits. And apparently more and more professional chefs are turning to induction, so they are in good company.
Marc Rosenbaum is director of engineering at South Mountain Company on the island of Martha’s Vineyard in Massachusetts. He writes a blog called Thriving on Low Carbon.