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electric kettle vs stove top

 
paul wheaton
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A few years ago I got a little freaked out about stove top kettles that were forgotten and had melted, and fused themselves to the electric burner. 

So I bought this electric kettle



It has been an amazingly excellent experience.

It heats water about twice as fast as on the stove or in the microwave.  And I suspect that the amount of energy used to heat the water is probably about a third.

And that's the root of my question:  does it really use less energy?  I'm having trouble finding the final word.

As long as I'm advocating this thing:  It is glass - so no worries about plastics or odd metals leaching creepy stuff into the water.  Also, if anything gets gross inside, you can see it right away.  The large opening at the top is great for cleaning.  And, the best feature:  once the water is boiling, it turns itself off. 

 
paul wheaton
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Apparently, it uses 1500 watts. 

How many watts does a stovetop burner use on its highest setting?

 
                          
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dont know what a stove top uses but with electric kettle you can save power by only heating what you need as long as the element is covered, no need to fill kettle to top for only 1 coffee/tea
 
paul wheaton
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Brenda Groth
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well they do say the smaller the item you are heating the more efficient it will be if it fits the use needed..so it makes sense that an elec kettle would be efficient for it's use..if used normally.

just like an elec fry pan is useful as it only heats what is in the pan..

however..i have a gas stove..so it isn't likely that it would be useful for me..as propane is cheaper for me to use than electricity.

i do think some elec appliances are money savers if properly used ..however..if the power goes out..you are up a creek..that is where propane works better for me.
 
Joel Hollingsworth
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If you have an electric stove, your kettle uses much, much less heat.

It is also definitely less than a microwave would use for the same task.

As far as total energy from the source to the coffee, it might break even with a gas stove, or be better or worse, depending on local circumstances.
 
paul wheaton
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My shooting-from-the-hip math says that the kettle above uses about one third the energy of an electric stovetop. 

Data I have collected so far:  the stovetop uses 2500 watts when on high.  The kettle uses 1500 watts.  And, I think the kettle heats the same amount of water in about half the time.   

So the amount of time difference is the part that is a guess so far.

Assuming that that one guess is accurate, then this kettle uses 30 cents on the dollar that the stovetop approach uses. 

Supposing that somebody boils water 4 times a day and it take seven minutes each time ....  12.5 cents per kwh ......  7 * 4 * 365 = 10,220 minutes in a year .... divided by 60 is 170.33 hours in a year ...  2500 watts in an hour would be 2.5kwh ....  2.5kwh * 170.33 * $0.125/kwh = $53.23 per year when using the stove. 

Then using this standalone kettle would give a savings of $37.26 per year. 





 
paul wheaton
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To get better answers I needed tests.  

I know that Jocelyn has both kinds of kettles.  She told me that she has an 8 inch electric burner.  My previous number was for a 9 inch burner.  In checking around, 8 inch burners use 2000 to 2450 watts.  I don't know exactly what Jocelyn's burner uses, but I'll just go with an average of 2250 and confess that all of the numbers are +/- 10%

She tried exactly four cups of water in each.  On the first pass she compared where the stove top kettle whistled to when the plug-in kettle turned itself off due to a rolling boil.  I asked her to double check when the stove top reached a rolling boil.

4:36 plug-in kettle
5:14 burner kettle

So, the burner was 314 seconds and the plug-in was 38 second faster.   The plug-in used 33% less power.  

314*2250=706,500

280*1500=420,000

difference = 286,500

So, you could say that the stove top uses 68% more power to boil water.  

Re-doing the other math ....   4 times per day at 314 seconds each time.  4 * 314 * 365 = 458,440 seconds.  Which is 127.34 hours per year.  Time 2250 watts is  286.5 kwh.  Time 12.5 cents per kwh is $35.81.  

35.81        x
-------  = ------
706.5      420

x = 21.29

Therefore, using the plug-in kettle would save $14.52 per year.  


 
Joel Hollingsworth
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Hooray for science! 
 
Jocelyn Campbell
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So a new electric kettle will pay for itself in about four years?   

There are human factors to consider, too. How often is the burner left on after the stove top kettle whistles? A lot of times folks aren't right there, ready to turn it off, so the power use differences could be even larger.

Additionally, I tend to use any leftover hot water in the electric kettle much more than I ever did from the stove top tea kettle. For washing dishes, for the bit of water in my basted eggs, for rinsing out a hot pan. It saves me a lot of running the tap water until it's hot.

Maybe I think of it and use it more because I can see the water inside, or because of where I have it plugged in. Or, it could be that it pours easier out of the electric kettle - you don't have to use a button or lever to pull the whistle off the spout. 

In non-scientific summary, and regardless of the savings, I simply like the electric kettle better. 
 
paul wheaton
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For me, even if the energy usage was the same, I would still like this kettle better.  The whole kettle fused to the burner thing left me in a pretty uneasy position. 
 
                                  
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You could also drink green tea which is best when the water is heated to about 185 degrees instead of boiling. And/or move to Denver, where water boils at a lower temperature. 
 
Emerson White
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Moving to Denver would actually make the problem worse. Since you are up high the lower pressure means that the Vapor pressure of the water climbs above the ambient pressure at a lower temperature, so you loose energy to the phase change sooner. In Denver while the water may boil faster the tea still needs the same steeping temp. I realize that it was a joke, but it was wrong, so I had to crush your fun. I'm sorry, that's how science works :p.
 
                                  
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Emerson White wrote:
In Denver while the water may boil faster the tea still needs the same steeping temp.


As a practical matter, it actually doesn't.  If it were true, you wouldn't be able to make a good cup of tea in Denver.  People at high altitudes compensate for the decreased boiling temperature by increased brewing time and, if necessary, a bit more tea in the pot.  As a tea fanatic, over the years I've experimented with different brewing temperatures of black, green, white, puerh and compressed teas.  Black tea does fine at temps a bit lower than 212.  But I sympathize.  Sometimes it's best to leave a joke as a joke.  :p

(See more about how people compensate for high altitudes at: http://www.ext.colostate.edu/pubs/foodnut/p41.html#cook)
 
Emerson White
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As a tea fanatic who spent 4 and a half years living at 7,2 in Durango I am well familiar with the subject. the optimum steeping temperature is going to be somewhere between 175 and 200 depending on the variety of tea you are consuming. Boiling point at 5,2 is 202F while the boiling point at 7,200 is 198F.

There is no tea (maybe a tissane of some sort) that should be boiled.
 
Emerson White
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A further question, how does this model look for cooking in the kettle? I often used my previous kettle to cook Raman or boil up dry morels in chicken stock (when I made it) and it had a groove around the top that made it very difficult to clean.
 
paul wheaton
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I suppose one could - but I think it would be poorly suited for it.  Due to the narrower top.
 
Max Kennedy
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The plug in, all the heating element is immersed in the water.  No matter the design stovetop heating radiates heat to the air, the surrounding surfaces and has to pass through the metal of the Kettle for convective losses.  The electric kettle is more efficient than stovetop with the caveate that if you have a RMH heating the kettle on top of the drum is more efficient than either as you would be heating the room with the heat anyway.
 
                                  
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Emerson White wrote:
As a tea fanatic who spent 4 and a half years living at 7,2 in Durango I am well familiar with the subject. the optimum steeping temperature is going to be somewhere between 175 and 200 depending on the variety of tea you are consuming. Boiling point at 5,2 is 202F while the boiling point at 7,200 is 198F.
There is no tea (maybe a tissane of some sort) that should be boiled.


Who's saying boil the tea  Most authorities would say simply to infuse with boiling water, and only for blacks and puers.  And in my experience that's generally correct, all else equal (and it rarely is), although I've also had success steeping some blacks with below-boiling temperatures.

In addition, not only variety, but also whether it's a first flush up to fourth flush picking, and first infusion to subsequent infusion (something not generally recommended for blacks except for puers).  Flavor profiles will differ, sometimes markedly, for each.  It's much more an art than science, and I would question the advisability of specifying precise temperatures.
 
Emerson White
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No one is saying to boil the tea. However you have to get the water up to steeping temp's before you infuse the tea with it, and if boiling point is below steeping temp you cannot get the water hot enough for a good steep. My point was that you have to be very high in the mountains in order to hit that point.
 
                    
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Did you know that if you live in Missoula Mt. you can go to the MUD (Missoula Urban Demonstration project) tool library & check out a device to measure exactly how much power something is using?

You  could measure both the electric & Electric stove top consumption of power if you like.

D
 
                                
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Hi all,

Thanks for posing this interesting question. Actually this discussion is missing a whole vital element. unless you are supplying your power needs strictly from renewables, since a great deal of energy is lost in the power plant during the conversion from some form of fossil fuel (gas, coal, whatever) and afterwards the transportation also entails energy loss. the answer is that they actually come up to about the same.

This physics professor called David MacKay did the experiment & math for us in his awesome blog:
http://www.inference.phy.cam.ac.uk/sustainable/hotwater/ ;

his conclusion has been that it depends on whether it is summer or winter. summer go with electric, winter go with gas

I'd say the only thing he didn't account for is the energy required to process and transport gas. but then again this is valid in both the power plant electricity and gas power, so it kind of cancels out.

also another great tip i gleaned somewhere (don't remember where so unfortunately i can't provide the credit) is to fill a cup with water, pour it into your kettle, mark the height on the outside of the kettle, and presto, henceforth you only boil the amount of water you need.


anyway check out his site, there are other interesting questions answered like: does it make a difference if i boil water with the lid on or not.


 
Len Ovens
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drarbib wrote:
Thanks for posing this interesting question. Actually this discussion is missing a whole vital element. unless you are supplying your power needs strictly from renewables, since a great deal of energy is lost in the power plant during the conversion from some form of fossil fuel (gas, coal, whatever) and afterwards the transportation also entails energy loss. the answer is that they actually come up to about the same.

But I only pay for the power that makes it past my meter... no matter how much of it the power co uses to get it there... I accept their waste so long as I buy their product for any purpose.


his conclusion has been that it depends on whether it is summer or winter. summer go with electric, winter go with gas


Gas puts toxins into the house air. "Natural gas" contains a lot more than methane. It is an open flame where the exhaust enters the home. A wood stove is better... if it is designed to get the most out of the heat generated by the wood and not run it up the flue. I like how gas heats, but I don't like the exhaust thing or the inefficiency. Gas hobs being 40 to 50% and electric being 50 to 60%... our induction hobs at 1400watts seem to be as fast as gas at 90%. I personally think that the plugin kettle is the best. The element is in the water and often the kettle is somewhat insulated so the water stays warm for a longer time... often meaning that second cup takes no energy at all.


I'd say the only thing he didn't account for is the energy required to process and transport gas. but then again this is valid in both the power plant electricity and gas power, so it kind of cancels out.

also another great tip i gleaned somewhere (don't remember where so unfortunately i can't provide the credit) is to fill a cup with water, pour it into your kettle, mark the height on the outside of the kettle, and presto, henceforth you only boil the amount of water you need.


anyway check out his site, there are other interesting questions answered like: does it make a difference if i boil water with the lid on or not.



 
jenny penny
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This is our compromise...
http://www.amazon.com/Sunbeam-6131-Water-Dispenser-Black/dp/B000C3QSPQ/ref=sr_1_1?ie=UTF8&qid=1317419141&sr=8-1

It heats up to 2 cups of water. You can just fill your mug, dump the water in, and heat. It shuts off immediately when it's done. You only heat the exact amount of water you need. Caveat--you can't fit tall mugs (like travel mugs) under the dispenser. You have to use a regular mug and transfer.
 
Len Ovens
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jennypenny wrote:
This is our compromise...
http://www.amazon.com/Sunbeam-6131-Water-Dispenser-Black/dp/B000C3QSPQ/ref=sr_1_1?ie=UTF8&qid=1317419141&sr=8-1

It heats up to 2 cups of water. You can just fill your mug, dump the water in, and heat. It shuts off immediately when it's done. You only heat the exact amount of water you need. Caveat--you can't fit tall mugs (like travel mugs) under the dispenser. You have to use a regular mug and transfer.


A coffee maker might be cheaper ($7 for a 6 cup $13 for a 12 cup) and without the filter in the way, the tall mug would fit. However, it does have to be turned off... it would try to keep the mug warm. Our water fountain has a hot function... but it has to be turned off when not in use and never boils. The heater you have looks like a good contraption.
 
Scott Perkins
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I see what was left out of the equations was the initial cost of an electric stovetop. If you also switched to electric skillets and waffle irons
and George Forman electric grills etc and never got the stove in the first place, there would likely be a savings of many hundreds of dollars and maybe get to a thousand or more.

Aw we know, what we pay for most everything is directly tied to the convenience of use as well as the actual product or benefit of use.
And we pretty much know that more convenience equals more cost
 
Gary Wolfer
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This is my first post here. I love your site. Much info like the old Mother Earth news. On the subject of Electric tea pots. My wife twice welded a metal tea pot to the burner. Burners are often more expensive than tea pots. We have had an electric tea pot since the second mishap. Been a long time now. I am searching for a new tea pot now as we are living in a motorhome and moving from place to place. We have accumulated a lot of calcium deposits in the bottom and sides of the metal electric pot. The problem is the opening is too small to get an average hand in to clean. I soaked it and boiled it with vinegar and baking soda more times than I can remember and scrubbed it with a scouring pad with a wooden spoon from the top but never get the pot clean. On the subject of heating other things my wife uses it to fill cup of soups and ramen noodles and my son even boils water then dumps it into a pan on the stove to quickly boil water for mac and cheese. Actually preheating water for a pan on the stove is another good use. Now I am going searching other threads I am in heaven.
 
John Polk
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Here is a link with info on removing mineral deposits.
One thing mentioned is phosphoric acid. Coke and Pepsi have enough phos. acid to remove rust...it also softens calcium scale.

http://www.bae.ncsu.edu/programs/extension/publicat/wqwm/he397.html
 
Eric Gold
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First time poster here -- Hello all !

The radiant elements in stoves or kettles are close to 100% efficient, meaning all the energy is turned into heat. The differences, if any, during heating occur if some of the heat is lost to the surroundings rather than going into the water. Surroundings can be the container the water is in, or the environment. Microwaves come very close to converting 100% of electricity to heat that does go into the water container and water. This is as good as it gets if the heat source is electricity.

Conclusion #1: if you are using a stove-top, try to use a pot that covers the entire heating surface. If you prefer a kettle, buy an well-insulated one.

Second, any heated water not used is wasted. Even if it is used later, the amount it cooled down is wasted. This is the problem with kettles that keep the water warm -- heat is lost continuously from the less than perfectly insulated kettle.

Conclusion #2: Heat up only what you are using right now.

My choice: I heat up one cup at a time in the microwave.

Theoretical best option: if you have tap hot water from natural gas, fill up a thermos with hot water from the tap. Microwave the amount you are using right now for a few seconds to bring it to boiling. I say theoretical because one usually has to account for the wasted heat going down the drain until the water is hot. However, if you have a habit say of washing dishes in warm water, you could fill thermos at that time and avoid the warm-up penalty. Nowadays I pay 11 cents a kwh for electricity, and 2.4 cents a kwh for natural gas. My local boiler is 67% efficient, so my actual cost to add a kwh of energy to water is 2.4/0.67 = 3.6 cents a kwh. A decent thermos probably will retain 80% of heat for 6 hours (my guess,) so the cost per kwh using tap hot water is 3.6/0.8 = 4.5 cents -- less than half of electricity.

For those interested in environmental cost, natural gas tends to be a much preferred source to heat stuff up than electricity because grid electricity usually has a large component of coal, and central power plants are in general only one half as thermally efficient as a natural gas burner in our homes.
 
I agree. Here's the link: http://stoves2.com
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