goodbye slow cooker, hello thermal cooker – hack thermal cooking and save

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Save electricity with a DIY Thermal CookerSlow cookers are great. You get home after a long day and there’s dinner, all ready and waiting for you.

You save time and you save money with a home cooked meal.

But what’s better than a slow cooker?

A thermal cooker.


Because it uses very little electricity.

In fact, after an initial heating of food, it uses no power at all!

Here’s how thermal cooking works.

Thermal cooking involves heating food on a conventional stove until it comes to the boil, then removing it from the heat and insulating it so that it continues to cook using residual heat rather than direct heat.

This method of cooking dates back thousands of years and is still used all over the world everyday, especially in places where fuel is expensive. Food is brought up to temperature on a convention stove (or over a fire) and then insulated. We can use blankets and towels to insulate our pot, but in the past hay, grasses, moss or dry leaves or water were used or the pot would be buried in the dirt.

The heat in the pot is thus conserved, and food cooks slowly, without the need for supervision, saving on fuel and time.

Unlike solar cooking, you can cook food regardless of whether there is sun or not. Put your oats in the thermal cooker in the evening and wake up to porridge for breakfast – all without the constant use of electricity.

A thermal cooker is also invaluable when camping or during times of extended power outages when you want to conserve the fuel of the camp stove.

While you can buy a commercial thermal cooker, they’re not cheap. Instead, you can DIY your own thermal cooker for free and get the same benefits as the commercial one.

DIY Thermal Cooker

All you need is an empty laundry basket or cardboard box or esky and some spare towels and or blankets.

Voila. You have yourself a thermal cooker.

And when the cooking is done, you don’t need to find room for another kitchen gadget.

Simply line the bottom of your basket or box with a blanket (actually, I like to use an old pillow), wrap your pot up in a towel and then insulate the sides of the box and around your pot well with blankets or towels. Heat will escape out the top if it can, so make sure you insulate the top well too.

To give you an idea of the effectiveness of this makeshift thermal cooker, I cooked beans in it the other day and not only were they perfectly cooked but they were still steaming when I drained them after 12 hours in the thermal cooker.

How to use your thermal cooker

While you can cook meats and casseroles in your thermal cooker, it’s a good idea to start with something simple. Check out the article on how to easily cook beans in the thermal cooker as an example.

Bring your food to the boil and boil or simmer it for a few minutes, depending on the size of the food. Beans can be boiled for 2 – 4 minutes. Meat will need to be boiled for around 10 – 15 minutes. What you need to do is bring the internal temperature of each piece of food in the pot to 60°C or more. It needs to be hot all the way through.

Once you’ve boiled your food, place the lid on, turn off the heat and put the pot straight into your thermal cooker and insulate it well. Then just leave it to continue to cook between 6 and 12 hours.

A thermal cooker is like a slow cooker, but with benefits. Because there’s no electricity it’s portable. In fact, it works just like a meal-sized flask.

Save time and save electricity with a thermal cooker. No need to buy a commercial one, DIY your own for free.

Have you used a thermal cooker? What have you cooked in it?

If you’re looking for more ways to save time and money when cooking, check out the Plan Cook Save eBook.

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  1. georgiaclaire says:

    Do you think this method could reasonably be used when canning fruit? I’m curious.

    1. Melissa Goodwin says:

      I wouldn’t with canning stuff. We don’t tend to process foods in Australia like in the US, so I’m not sure, but I understand you have to be precise when processing preserves.

      Anyone else with more experience with canning want to chime in on this one??

      1. DeerFarmer says:

        I (like most Australians that preserve) use water bath processing (I use a Fowler’s unit) instead of pressure-canning, and I wouldn’t be brave enough to use a thermal cooker as a replacement for this. Water bath processing depends on slowly increasing temperature to achieve a set temperature in the water (85 *C is a common one) for at least five minutes, at which point bacteria will be killed and a vacuum seal will develop with the slow cooling which occurs (note: this method only works for high acid, high sugar or high salt content, which ensures no clostridial spores remain, such as those responsible for botulism)

        I wouldn’t trust a thermal cooker to provide sufficiently even heating and to produce a reliably high enough temperature to ensure preservation for years. Not saying that it couldn’t, but I would like to use a method that makes me a little more certain .

        Hope this helps.

        1. Melissa Goodwin says:

          Thanks for your input DeerFarmer :).

    2. Lesleigh Edwards says:

      I had enough apricots left for one jar of preserved fruit so… I boiled some water and put it in my thermo pot. Boiled some more while I prepared the jar of fruit. I then emptied out the first lot of water and put some of the freshly boiled water in the pot , placed the jar of fruit into it and poured the water to go right up to the bottom of the jars lid. Closed the Thermo lid and left it for ages. Later that evening I took it out . The water was till hot and the jar had sealed perfectly. Note: I only did one jar so I’m not sure how two or more would go.
      Cheers Lesleigh

      1. Melissa Goodwin says:

        Hi. Yum! Thanks for sharing Lesleigh! Good to hear you got a good seal with the thermo.

  2. I always use this method for cooking corned silverside, one is wrapped up right now cooking, but I just leave it on the bench it’s not in a box or anything. It’s how my mum did it. I haven’t tried anything else. Would love to thought, not sure where I would start.

  3. I have an old real wool blanket, would this be good to wrap the pot in?

    1. Melissa Goodwin says:

      Yes! It would be perfect.