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Jon Freise


Fantastic article! I just discovered fireless cooking using an old Stanley Thermos to cook oat groats for breakfast. It cooks overnight, always works perfectly, never boils over, and even works in a hotel room with an electric kettle. We hardly cook oatmeal any other way.

You bring up Low-E glass coatings for solar box ovens. I wonder if the vacuum insulated glass might be an ideal application. The glass has visual distortions, but that would not be an issue with solar cookers.



Sounds a bit like the cooler sous vide cooking technique. Put some food in a ziploc, put some hot water in a cooler, place ziploc in, and wait.


works very well. Alas, it can be wasteful of water, but you can always re-use it for drinking, cleaning, etc.

Poul-Henning Kamp


Electrical induction deserves a closer look.

Since there are no particular hot parts near the pot, you can in principle wrap your pot in textile insulation while you cook without fire-risk.

Spills will still be a mess though, but we can do better:

Induction pots could have a a radiation shield ("Calorimeter principle") insulation: The exterior wall made from non-magnetic metal, such as aluminum or brass, the interior pot from iron.

Done right, such an "insulated induction pot" would not appear different from most common cooking pots today, and can even be put into dishwashers etc.

Claire Leavey


Lovely article. I've written about these (and fuel efficiency in general) in 'How to run a Thrifty Kitchen'! http://www.retrometro.co/shop/how-to-run-a-thrifty-kitchen.html

Lloyd Alter


The toledo cooker was very popular a hundred years ago in America, and there are still versions being made http://www.treehugger.com/kitchen-design/nissan-thermal-cooker-crockpot-without-cord.html



What about slow cookers or crock pots? Similar to the fireless cooking, but electrical. Not insulated, but if you have a slow cooker, you could build a hot box in which to put it. Once you know how long the crock pot takes to bring the contents up to a boil, you could plug it into a timer.

The crock pot cord goes through a hole punched in the bottom of the hot box, plugs into a timer. The timer turns off the crock pot after 2 hours (or however long it takes for the pot to get up to a boil).



Like this article series! Well done!
Also liking Poul-Henning Kamps comment. Sounds interesting.

A field for further studies is obviously camp stoves where fuel efficiency is a big factor, and the designs reflect that fact.

Insulation for a camping cook pot is commonly called a "pot cozy" and varies from retail neoprene versions to homemade bubble wrap contraptions. Could be something for home use as well.

The pot skirt concept is well utilized in the Trangia type of stoves, where the windshield of the stove goes a way up the sides of the pot. There are others as well.

kris de decker


@ Poul-Henning

Good point. Induction stoves lend themselves perfectly for integration with fireless cookers, in the spirit of the hybrid systems from the early twentieth century. An insulated cooking pot would reduce both heat transfer loss and power conversion losses and thus increase thermal efficiency.

@ Lloyd

Some fireless cookers were indeed equipped with soapstones. But the efficiency of this approach very much depends on how you heat the soapstones. If you do that in an oven, I'm afraid there's no advantage to it because ovens are less efficient than gas or electric hobs. But if you could use some source of waste heat it could be very worthwhile.

@ pond

As you say, a crock pot or slow cooker is not insulated, so that's a clear disadvantage compared to a fireless cooker. But if you put it in an insulated box, I guess you have what you need to cook more efficiently. Only I would feel more at ease leaving the house when the fireless cooker is cooking than when the insulated crock pot is cooking.



Like improved biomass stoves and fireless cookers, solar cookers are mainly promoted in developing countries as an alternative to the use of open fires.

Note that developing coutries have on average more sunshine than developed ones. They are generally closer to the equator.

One thing the article doesn't mention is why insulated cookers fell from favour.

David Wilson


If I understand the fireless cooker, the traditional Hawaiian imu would qualify as an industrial-strength fireless cooker. A wood fire heats rocks, which are then placed in and around the food in a covered pit. My wife's family cooks this way for luaus on the Big Island. I don't know how efficient it is, but the results taste fabulous.

Wikipedia has a good description in an article on kalua cooking: http://en.wikipedia.org/wiki/Kalua

Tim Barker


Hi Chris great article. It was good to see someone make the link between pressure cookers and retained heat cooking , we have used such a system in the past with very good results. Pressure cookers and solar also are a good combination but older pressure cookers with a bobble weight are better as the new ones require quite a head of stem to initially seal. At the Koanga institute where i do some work on Appropriate technology we did some tests with retained heat cookers where we installed the heating element out of an old slow cooker (approx 170 watts) and added a thermostat out of a hot water system which matches the heat range required well. Quite literally our hot box was an old solar oven with an insulated lid substituted for the glass and the heating element was sandwiched to the bottom of the bottom tray with a strip of aluminium. Our testing showed a minimum of 70% reduction in electricity used. Such a system if well built brings up some interesting possabilities as it could be used as a hot box, solar oven, or slow cooker and would cope very well in difficult climates. Worth mentioning also is the cooking pots themselves. Wide bases and good conductivity (tinned copper pots) over smaller footprint heating sources are the go.
Cheers Tim

Mark McClure


I enjoyed the article very much.

I have a 6-liter vacuum thermal cooker. One drawback to this device is that the pot needs to be fairly full in order to provide the thermal mass to see the cooking process to conclusion. I have thought of adding stones or big stainless steel ball bearings to the pot to provide the thermal mass when I am cooking only for two.

Regarding the pot skirt, I have thought of using galvanized steel duct parts to use as a sleeve, but I worry about the zinc oxide fumes that may develop when heating on a gas stove.

greg blonder


An excellent review, and a reminder that the biggest deposit of fossil fuels in the world are energy efficiency improvements under our control.

Sadly, when I was in high school in the 70s I wrote a similar paper in response to the OPEC energy crisis. Even had a chance to cook on a deep-well stove. With the enthusiasm of a teenager, boldly predicted all new stoves would consume 1/3rd the energy in 15 years. Ah well.

Note an electric crock pot with decent insulation and a feedback controller is quite efficient, and bridges the gap between fireless insulated pots and the oven. But most are pieces of junk. Conversion efficiencies do put electricity at a disadvantage, but co-gen and community power can bring it back in line.

Also, WHAT you cook matters, and it is hard to shift cultural tastes. Steaming veggies can take 1/3rd the energy of boiling, if you only steam the minimum amount of water required. But people often grow up the taste and texture of boiled.

David Karger


Here's another innovation: fins on the pot to collect extra heat from the flame: http://www.latimes.com/food/dailydish/la-dd-saucepan-rocket-scientist-heat-efficient-20140710-story.html

Mario Stoltz


Hello Chris,

Really enjoyed this and the previous article on cooking efficiency. Like Greg has commented, I would also think that the cooking style and the ingredients used make a difference. Not every cooking style corresponds well to more efficient methods of cooking / stoves. And here may be the main catch, in fact.

Slow cookers seem to correspond well to Foods that can cook for a longer time unattended, and where you do not have to stir and look all the time. Note that this also applies to steam cookers, for example - you have to be fairly sure about your cooking time in advance.

This may be the very reason why steam cookers are not very successful on a broad scale: not everyone is sufficiently confident in their cooking skills, or even cooks regularly at all. The food industry is trying to convince us that cooking is so difficult that we should rather buy their pre-fab / "semi-finished" foods and only warm them up.
To get this ball rolling seriously, both cooking Hardware and people's mindset about cooking must be changed.

kris de decker


@ Greg & Mario

What you cook indeed matters. It should also be noted that water is a more efficient heat transfer medium than oil, while oil is a more efficient heat transfer medium than air. Therefore, boiling food is always more efficient than frying or baking it.

In fact, when it comes to carbon emissions, the diet is more important than the cooking technology. For instance, boiling meat is more carbon intensive than frying vegetables, because meat production is inefficient.

@ Tim & David

Cooking pot design is important, too. Material, shape, color. I've seen a similar finned pot for use in a solar box cooker.

Etienne Bayenet


Very good article. I used the fireless cooker to sterilise water in Colombia. Works very well.

Etienne Bayenet



I also wrote an article (in French) about saving energy while cooking. The concept in the article is that reducing waste does not reduce our comfort, so I wanted to explain where energy is wasted. I didn't know about the fireless cooker when I wrote it.

You will find it with another about drying clothes on this page.

Since I found this article about insulated cooking pot great, I also added a link to it.

Best regards,

Etienne Bayenet

Pete Sherwood



Have you found any references to using (or not) cast iron in/with fireless cooking?
Although getting the cast iron up to temperature takes longer, it seems to be the perfect match for the retention of heat in the fireless box.
I've seen no mention of this in the several articles I've read.

Mario Stoltz


Hello Kris,
your article made a concrete difference in my camping vacation in Sweden this summer. I used a Trangia cooker (works on alcohol). Already in a past year, I built myself a windscreen in 6 segments from 1mm aluminium plate and hinge ribbons. So far, I have only used this by forming a U-shaped windscreen around the cooker with the opening facing away from the wind.
This year, I have closed the screen around the cooker (a fairly snug fit, though just by accident) and tried to put a partial lid on top if I had any suitable objects at hand. The difference in cooking time was immediately obvious. I have no measurement but would estimate at least 20% shorter time to get water to boiling point, even with such a rudimentary insulation. Thanks a lot!!



I'm rather surprised nobody has made mention of Rice Cooker appliances yet. Any halfway decent one will be insulated. You can touch the outside of it and it will be cooler than the surface of a car on a hot summer day, while rice is boiling inside. They are popular in Asian countries where energy is more expensive (phils for instance). They are also very cheap (I think I paid $20 for mine). Very handy appliance!



As one commenter just mentioned, the ole stanley thermos is my standard in fireless cookery. Metal model only please. Great for anything that will fit the small mouth opening. Done soups, stews, rice, etc this way.



To slow cook beans, lentils etc., I bring a pressure cooker to the boil, take it off the heat and wrap it in an old down jacket for a few hours. Works a treat.

Martin Zvieger


Great article

Three years ago I arrived at the idea to search for vaccum insulated cookware. Strange that the idea of the vaccum flask has never been applied to pots.

Swiss company Kuhn-Rikon offers a product line of doubled walled pots called Durotherm. http://www.kuhnrikonshop.com/category/energy-efficient-cookware-durotherm

It's a convenient alternative to fireless cooking as you start saving energy in the heating phase.

From questions posted on the Internet I jump to the conclusion that there is demand for highly optimized cookware, what's missing is an industry jumping up the bandwagon.

Take cheap rice cookers - which are operated in the zillions. What a waste - we can build them near thermodynamic optimum and make them last for generations.



I agree transferring a heated pot to cold insulation is not ideal.
It would be so much better if pot and heating element were well insulated.
I have long wanted to try a base heating element and pot sides, both completely enclosed in vacuum insulation.



I wrapped a large stock pot with an old towel to use on an under sized electric burner for boiling several gallons of water at once. It brought the water to a boil in notably less time and would maintain the boiling when I took the lid off. Encouraged I then spread another towel over the top and it again boiled much sooner and much more energetically. I am looking for expanding foam suitable for sealing around fireplaces for a permanent fix.



I have an antique (80 year old) Faultless Fireless Cooker made by the Diller Manufacturing Co. which is complete and still cooks very well.

But it is not as efficient as my 6 liter Thermos Shuttle Chef that has two 3 liter cooking pots and one 6 liter cooking pot. We use the Shuttle Chef at least once a week and find it indispensable in our kitchen.

A previous comment mentions the problems with small amounts of food not having enough thermal mass to cook food adequately which I would like to address:

One solution is to plan a meal that has rice in addition to the main course. For example I cook chicken tikki masala in one 3 liter pot and basmati rice in the other 3 liter pot.
Another solution is to cook spaghetti sauce in one 3 liter pot and fill the other 3 liter pot with boiling water. When the sauce is cooked I put the water pot back on the stove to cook the pasta - it typically takes less than 2 minutes to bring the water back to boiling!
Another solution is to use the pot of hot water to wash the dishes afterwards.

The 6 liter cooking pot I find is best suited and ideal for cooking large batches of chili, soups, stews, etc.

If you are interested there as some very informative videos for the Shuttle Chef on YouTube. Search "MrDsKitchen" or Shuttle Chef. I should also mention that the Thermos Shuttle Chef is great for camping and boating.

I am not affiliated with Thermos. Just a very happy user.


Elmo Dutra Filho


Congrats Kris!!! Excelent article! Wonderful graphics, images. I was looking for that!

I've been using heat retention for years, and decided to write about it! I use solar and pressure cooker, plus heat retention box I did six years ago! Still working! White rice I can prepare with only one minute in pressure cooker (steam) plus 35 minutes in heat retention box. Beans I can prepare in two times, only 2 (two) minutes of pressure (steam) plus two periods of 35 minutes. I said two minutes of steam!

I'm from Brazil, webmaster of site www.fogaosolar.net , mechanical engineer and professor. In my country, unfortunatly, we don't use heat retention! I would like to show this advantages to poor comunitys in my country. Thanks for this oportunity. Excuse for my bad english!

Stewart MacLachlan


This is probably one of the very best articles in a crowded field at low tech magazine. I keep returning for a read. It could do with being reposted at the top of the list.

As an enthusiast of solar and integrated cooking, which I promote here in the UK on a shoestring, it touches on these subjects brilliantly, cooking efficiency is low hanging fruit for energy efficiency. developments in solar cooking are moving fast, but it's mostly unknown and unconsidered, compared to big ticket items like solar PV, or even solar garden lights - instant landfill!

My website is www.slicksolarstove.com if anybody is interested in how we've been getting on.
And also www.ecozoom-uk.com for rocket stoves, just need something for heat retention and I've got the set,

Thanks to Kris for the great site !



there are also great looking
Flameless gas hobs

Beautiful ceramic appearance, modern design, saving up to 50% on energy bills for gas and safety at a high level. Meet our invention and let yourself be inspire.



This is an interesting example of a solar cooker that uses vacuum insulated glass and a parabolic reflector: http://www.gosunstove.com/



In the past 30 years, I have NEVER read an article that measures the inefficiency of a human scavanging wood or dung and carrying it to a fire.

The time value of that work, the calories expended, the human drudgery, seem to me to be on a par with the net efficiency of an electric power grid.

Mark McClure


One more energy-saving cooking device is the "cooking pin." It is basically a sealed tube, partially filled with liquid. The chef would insert the pin half way into a roast and then cook in the oven. The pin would transfer heat to the center of the roast for quicker cooking.

And I remember my mother had thick aluminum nails, which she would insert 1/2 way into potatoes to make them bake faster. (Pre-microwave days.)

Adriana Botello


Hebbel cellular concrete is an outstanding insulator, and easy to work with.

Ann Ellis


You didn't mention the efficiency of what you are cooking, such as meat vs vegetables.
Also no mention of the raw diet. Doesn't this save fuel?

priscilla miller


this has been interesting and helpful. i was remembering stories of how folks long ago would use a fireless cooker for hot food after a long day at the county fair, or traveling in a wagon all day, harvest time or just a church gathering or picnic. it would be a wooden box, thick insulation such as straw and quilts and a strong guy to lift it all in the wagon or trunk of the car. after cooking all day, the family would have a hot meal that no one had to stand over and cook or get more fuel or get burned. sounds good to me!

Levitan Gallarde





The link to the "An Investigation of Skirts" paper is outdated. Old link in the text:


I found new links only on archive.org:





@ Poul-Henning

Careful, because induction can be a fire hazard too. Do not put fabrics close to the base of a pot on an induction stove. People have a sense of security because induction cook-tops do not directly heat up, but an empty pan or pot can reach over 1000° if left unattended on an induction cook-top and even the solder from the base of the pot can melt out destroying the pot. In fact induction cook-tops can heat your pan hotter than any other cook-top. A pot left on an induction stove for too long, then taken outdoors and put on the ground, will easily start a grass fire and can even ignite wood chips.



@ Ann Ellis

Great point. Use the stove less and eat some raw food occasionally! Also switch off that second refrigerator. Storing lots of food or storing for long periods uses a lot of energy too.

Pete Schwartz


Love the article! At Cal Poly, my students and I invented and are developing Insulated Solar Electric Cooking (ISEC), which leverages insulation and the continuing decrease in cost of solar panels. Please read about our research here: http://sharedcurriculum.peteschwartz.net/solar-electric-cooking/

Or see this video we made last summer in Ghana: https://www.youtube.com/watch?v=vK-XyyHJaX4&



In 1990 I bought a dark brown insulated pot, it had a thick round rock that you heated in a camp fire, the insulated lid fit perfectly on top, had a yellow rope to wrap around the lid. It was insulated with some yellow hard stuff between outside and inside pan, reminded me of great stuff canned spray. This wasn't a homemade item, came with a book. It was awesome, cooked like crazy. The outside of the big pot had a texture. I wish I still had it. Has anyone come across anything like I'm describing???



Great article. Seems super useful for cooking beans.

During the winter when I am already running the gas furnace is there any energy lost by using more gas on the stove?

Pat MM


Great article! Thanks. I read this years ago and played with solar ovens for a few years, but we are surrounded by trees, making the solar oven difficult to use except in the summer when the sun is overhead. I need to revisit it, combined with the fireless cooker.
I remembered your article when I was listening to NPR. Here is a link to the NPR article about cooking boxes. Great stuff…




Would this work for cooking a turkey? Or would cooking in a pit dug in the dirt, like a pig, be better for a turkey? If a pot roast can be cooked this way, a turkey might work. Is a turkey so big that the heat might not last long enough to fully cook?

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