SAN FRANCISCO, 24 MAY 2009
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
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
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 www.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
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,
Michael Bluejay, www.michaelbluejay.com.
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