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Efficient Cooking

Posted on Apr 28 2009 by Alex Wilson

Which is better: a gas or electric range? Most serious cooks prefer gas, because it delivers heat instantly and is highly controllable. With typical electric cooktops, it takes longer for the burner to respond when turned on and when the setting is adjusted.

I used to be in the gas cooking camp. But I switched to electric nearly 20 years ago when my two daughters were very young, and I’ve been surprised at how satisfactory the electric cooking has been. My decision was fueled by studies I read back in the 1980s about possible long-term impacts of breathing gas combustion products in homes, particularly by children. Concerns include asthma, other respiratory ailments, and even (some studies suggested) effects on mental development and intelligence. So I’ve opted for an electric range for health reasons. But how does the energy performance compare? It’s actually quite interesting—at least for energy geeks!

When we’re comparing gas and electric space heating, gas is inherently more efficient — if we factor in the “source energy” used by utility companies to generate electricity. But if we consider only the “site energy” for heating, electricity comes out on top, because 100% of the power going into the heating element is converted into heat. With cooking, it’s more complex, because we have to consider the heat transfer from the heat source (a gas flame or electric element) into the food being cooked as well as energy that doesn’t actually contribute to the cooking.

With gas cooktops, it turns out that a lot of the energy content of the gas is not transferred to the food, so cooking efficiency is fairly low: about 40%, compared with 74% for electric, according to a study by Lawrence Berkeley National Laboratory (LBNL). If a gas cooktop has a pilot light, about half of the annual energy use is for the pilot, so the “Energy Factor” (an annualized measure of efficiency) is typically less than 20%. Smooth-top electric cooktops are slightly more efficient than the older-style electric-coil elements, but the difference is usually less than 1%.

Newer-style “induction cooktops” are more efficient: about 84%, because the electrical energy is transferred directly to the cooking vessel (which has to be ferrous metal that a magnet will stick to); unfortunately induction cooktops are still very expensive.

What about gas vs. electric ovens? Here, the argument for electric is even stronger. From a performance standpoint, rapid controllability isn’t as important with an oven as it is for a cooktop, and the temperature controls for electric ovens tend to be more accurate. Indeed, many gourmet cooks buy ranges that include gas cooktops and electric ovens for performance reasons. From an efficiency standpoint, gas ovens require a lot more air flow (to provide oxygen for combustion and to remove combustion gases from the oven compartment), so their efficiency is significantly lower.

A standard electric oven has a cooking efficiency of about 12%, according to the LBNL study, while a self-cleaning electric oven, which has more insulation in the oven case, has a cooking efficiency of about 14%. By comparison, standard gas ovens have cooking efficiencies of about 6% and self-cleaning models 7%. If the self-cleaning feature is used frequently in an oven, the Energy Factor drops, due to the energy use for self-cleaning. The electric clocks in both gas and electric ovens can significantly worsen the annual energy factor, since they consume an average of 4 watts and operate all the time. Pilot lights on old gas ovens dramatically reduce the annual energy factor.

Furthermore, a lot of people don’t realize that most gas ovens have electric “glow bars” that draw 350 to 500 watts the entire time the oven is operating. This is a safety feature to make sure that if the flame blows out for some reason, gas will not accumulate in the oven. While this is a lot less electricity than an electric oven, which draws several thousand watts, it’s almost as much as a microwave oven, and it has to operate longer than a microwave oven to do the same cooking. (The cooking efficiency of microwave ovens is about 56%—nearly ten times that of a standard gas oven and more than four times that of an electric oven.)

In other words, gas ovens may actually use more electricity than electric microwave ovens. And during a power outage, most gas ovens won’t operate at all (though gas cooktops can be used if started manually).

Below are few recommendations for saving energy when purchasing or using cooking equipment:

  • Buy a self-cleaning oven, but minimize use of the self-cleaning feature.
  • Buy a convection oven, which allows cooking at a lower temperature because the heat is more uniformly distributed.
  • Avoid buying an old gas range, cooktop, or oven that has a pilot light (pilot lights are no longer included on new cooking equipment)
  • Use a microwave oven for reheating food and for cooking when practical
  • Use a slow-cooker (Crock Pot or similar appliance) for stews, soups, and other dishes where single-container cooking is feasible; use a stand-alone rice cooker for rice.
  • With an electric cooktop, match the element diameter to the pot or pan. Using a 6-inch pan on an 8-inch element will waste 40% of the energy.
  • With an electric cooktop, make sure your pots and pans have flat bottoms to maximize heat transfer.
  • Keep your stove and oven clean to improve performance.
  • Defrost foods before cooking to reduce cooking time and energy use, unless cooking instructions suggest otherwise.
  • Optimize your cooking—for example, by cooking larger portions that can be used for several meals—and then reheat in a microwave oven as needed.
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The energy use for cooking—whether gas or electric—is a very small percentage of a home’s typical energy consumption (about 5%), so there are more important places to put your efforts, relative to savings. But every little bit helps.



1.
Sat, 05/01/2010 - 19:01

Another gas vs electric life cycle consideration to consider
by Dudley

Helpful? 0

Running the stove hood whenever using a gas oven can help remove unwanted water vapor and other combustion products from a home. I have been told that in some communities the hood fan .must automatically start when lighting a gas oven. Depending on what you are cooking and how you are cooking it, it is a good idea to use the stove hood fan even if you have an electric oven. But with a gas oven, just the water vapor from combustion can be a challenge in a tight home and even "clean-burning" gas is only relatively clean. When using a gas stove, the hood fan should ALWAYS be used and running the fan motor and conditioning the "make-up" air that replaces the exhausted air require additional energy if active space heating or cooling is happening. This additional use of energy further decreases the efficiency of a gas stove's function.


2.
Mon, 05/03/2010 - 16:48

I have a Magic Chef ceramic
by dj

Helpful? -1

I have a Magic Chef ceramic top. It keeps beeping w/an F1 code. I replaced the circuitry once, but it only lasted a year. So I currently turn the power off to the stove. This has had an added benefit: less electricity and I've learned to use other methods. I use a griddle and crock pot. In the summer I take them outside so I don't heat up the house. When I do need the oven, I turn the power on, and cook in batches and freeze. I'm going to delay buying a new stove as long as possible. It's a challenge/race now. :-)

I don't need bells and whistles. I just need heat. Ever try to find an appliance with few electronics. I thought my expensive Magic Chef would last me 20 years or more, like my parents appliances. But, I was told that the life span of a stove is 10 years now. Things might be less expensive upfront or have more bells and whistles, but maintenance is more, and the life span is less.


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