MICROWAVES--MAYBE: Microwaves are a tad more energy-efficient than gas burners, but about 25 percent less efficient than electric burners. They can save as much as 80 percent of the energy needed to cook or warm up food in the oven, but experts say that the energy used by all methods of cooking pales in comparison to that used in heating, cooling and lighting one's home as well as in the laundry room.
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Dear EarthTalk: How does the microwave compare in energy use, say, to using a gas or electric stove burner to heat water for a cup of tea?
-- Tempie, Dexter, MI
The short answer is that it depends upon several variables, including the price of electricity versus gas, and the relative efficiency of the appliances involved. Typically, though, a microwave would be slightly more efficient at heating water than the flame on a gas stove, and should use up a little less energy. The reason: The microwave’s heat waves are focused on the liquid (or food) inside, not on heating the air or container around it, meaning that most if not all of the energy generated is used to make your water ready.
Given this logic, it is hard to believe that a burner element on an electric stovetop would be any better, but an analysis by Home Energy Magazine found otherwise. The magazine’s researchers discovered that an electric burner uses about 25 percent less electricity than a microwave in boiling a cup of water.
That said, the difference in energy saved by using one method over another is negligible: Choosing the most efficient process might save a heavy tea drinker a dollar or so a year. “You’d save more energy over the year by replacing one light bulb with a CFL [compact fluorescent lightbulb] or turning off the air conditioner for an hour—not an hour a day, one hour at some point over the whole year,” says consumer advocate Michael Bluejay.
Although a microwave may not save much energy or money over a stove burner when heating water, it can be much more energy-efficient than a traditional full-size oven when it comes to cooking food. For starters, because their heat waves are concentrated on the food, microwaves cook and heat much faster than traditional ovens. According to the federal government’s Energy Star program, which rates appliances based on their energy-efficiency, cooking or re-heating small portions of food in the microwave can save as much as 80 percent of the energy used to cook or warm them up in the oven.
The website Treehugger.com reports that there are other things you can do to optimize your energy efficiency around the kitchen when cooking. For starters, make sure to keep the inside surfaces of your microwave oven clean so as to maximize the amount of energy reflected toward your food. On a gas stovetop, make sure the flame is fully below the cookware; likewise, on an electric stovetop, make sure the pan or kettle completely covers the heating element to minimize wasted heat. Also, use the appropriate size pan for the job at hand, as smaller pans are cheaper and more energy-efficient to heat up.
Despite these tips for cooking greener, Bluejay reiterates that most of us will hardly put a dent in our overall energy use just by choosing one appliance over another. According to his analysis, for someone who bakes three hours a week the cheapest cooking method saves only an estimated $2.06/month compared to the most expensive method.
“Focusing on cooking methods is not the way to save electricity [at home],” says Bluejay. “You should look at heating, cooling, lighting and laundry instead.”
CONTACTS: Home Energy Magazine, www.homeenergy.org; Treehugger, www.treehugger.com; Michael Bluejay, www.michaelbluejay.com.
EarthTalk is produced by E/The Environmental Magazine. SEND YOUR ENVIRONMENTAL QUESTIONS TO: EarthTalk, P.O. Box 5098, Westport, CT 06881; earthtalk@emagazine.com. Read past columns at: www.emagazine.com/earthtalk/archives.php. EarthTalk is now a book! Details and order information at: www.emagazine.com/earthtalkbook.
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9 Comments
Add CommentThis is why I think @sciam is so great. I have wondered this very question myself. This is a well researched and clearly explained article.
Reply | Report Abuse | Link to thisIronic, I think more energy was expended on the article, than any cumulative benefit it contributed to added efficiency. Im gonna go have some luke-warm tea, that should be energy efficient no matter how I make it.
@JeffACSH
Ok, so it's pointless to think about saving energy in cooking. But even so, I had the idea that induction cookers (http://en.wikipedia.org/wiki/Induction_cooker) were the most efficient of all methods to heat food.
Reply | Report Abuse | Link to thisIf I remember my physics correctly, electrical energy has already been "upgraded" from the heat value of the fuel to work. That may not be the best way to say it, but in converting the energy from gas to electricity, a significant portion is lost to waste heat as a necessary part of the process (think cooling towers). Therefore, from an energy standpoint going back to the source, it should be more efficient to heat water on a gas stove than via electricity. This would require a properly sized burner and pan to avoid significant heat loss to the ambient.
Reply | Report Abuse | Link to thisI can believe an electric stove is more efficient than a microwave in heating water. The electrical energy has to power a fan and a light in addition to pumping out microwave energy. The container is also important. The microwave may have had to heat up a heavy ceramic mug vs. a small thin pot on the stove.
One important variable is the amount of water being heated. At least in my experience a tea kettle heated on the stove is likely to have many times more water than is needed to make a cup of tea, while it is usual to use the microwave to heat the exact amount of water needed in the serving cup thus not unnecessarily heating additional water. Additionally, the additional heat put in the kettle will be transmitted into the room affecting the cooling costs for the house (I'm in Arizona).
Reply | Report Abuse | Link to thisAs a tea drinker (and Brit!) - how about an electric kettle - much quicker and I'm sure more efficient than either a microwave or stove top.
Reply | Report Abuse | Link to thisAs a tea drinker (and Brit!) - how about an electric kettle - much quicker and I'm sure more efficient than either a microwave or stove top.
Reply | Report Abuse | Link to thisMost of the lights I have are fluorescent. My electric bill for 3 computers,5 tv sets,kitchen light over sink always on, is about 1 $16.00 a month.
Reply | Report Abuse | Link to thisWhere do you live, and do you have an air conditioner/heater at all? (I live in Houston, TX and it is impossible not to cool one's house from about April to October -- not only because 80-100 degree heat is unbearable, but because the humidity would destroy clothing, furniture, carpets...)
Reply | Report Abuse | Link to thisOften I choose the conventional oven to cook a baked potato. I set the heat for 400 and cook for one hour. My family contends this is a waste of energy, compared to our microwave.
Reply | Report Abuse | Link to thisDoes anyone know the correct answer here? I maintain that in the regular oven, the power does not have to continually be on to maintain the set temperature of 400.
As an aside, I like to cook with the conventional oven, because this affords me the time to prepare or do other things....
Thanks,
Bill1278