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I am wanting to cook relatively small portions of dry beans but am not sure what kind of equipment to buy. My main concern is energy efficiency: I expect to cook a lot of individual portions over the coming years and know from experience that if I cook them conventionally, that this means hours and hours of cooking.

What would be the most energy efficient way to cook these beans? If it matters, let's assume batches of 400g kidney beans, and that they have been soaked overnight.

I have a gas stove and the options seem to be:

  • Boil them in a regular stainless steel pot
  • Using a cast iron pot (better heat retention?)
  • Slow cooker
  • Pressure cooker (on the stove)
  • Electric pressure cooker

Not sure if there are other common options (I don't have access to niche products). I found blogs such as these on the topic, but these seem to be personal blogs with data from single experiments, not sure how thorough or reliable this is.

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    IMO the most energy efficient way to cook them is not to do small batches, but to cook loads and freeze them fully cooked (as I do with my 3/4/5-bean chilli using a slow cooker). Then defrost 24h in the fridge and reheat in a microwave or on the stove
    – Chris H
    Nov 16 at 16:58
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    Neither a fridge nor freezer available
    – user74934
    Nov 16 at 16:59
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    Probably not really an option, but the most efficient way would probably be to use a solar oven. There's a recipe for beans in this introductory guide to solar cooking: commonsensehome.com/getting-started-with-solar-cooking
    – Juhasz
    Nov 16 at 17:26
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    @Joe I have a gas stove available. Gas is reliably available. As is electricity if I were to use an electric appliance.
    – user74934
    Nov 16 at 17:34
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    @Joe there may be a hybrid approach, of using a pressure cooker until not quite done, and then insulation
    – Chris H
    Nov 16 at 20:15
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With your constraints, and looking strictly at energy use, an electric pressure cooker would be the way to go. This is because unlike a stovetop pressure cooker they're insulated, even if only a little. Unlike a slow cooker there's less thermal mass of pot to heat up, and with kidney beans specifically, you need a hard boil as well as any slow cooking, to break down the Phytohaemagglutinin. This will add to the energy use of slow cooking.

If you know you're not going to switch to much larger batches, a smaller pressure cooker would be better than a larger one, as you need to create enough steam to pressurise the pot, meaning boiling more water for the larger pot.

In terms of carbon emissions and cost of energy, they may be better than a pressure cooker on a gas stove, or they may not. This depends on your local energy mix and pricing.

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  • Also very little steam escapes through the valve while cooking (at least on the Instant Pot I own) compared to a stovetop cooker (all the ones I've seen), so less need for water = less energy spent heating water = more efficient.
    – Luciano
    Nov 17 at 9:24
  • @Luciano it's a long time since I've used a stovetop one, and I've never used an electric one. But that seems like it could be variation between different models (I'm vaguely looking out for either sort 2nd hand though I don't really need another kitchen gadget or have the space)
    – Chris H
    Nov 17 at 9:33
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    it might be, but the stovetop version I use is quite modern as is the electric one, and even then it's a significant difference - I barely see any steam coming out of the electric model.
    – Luciano
    Nov 17 at 12:56
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A pressure cooker will be the quickest and most energy efficient option. Stove top or electric will probably depend on your available space and energy resources.

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  • Thanks. Do you have sources for this? How exactly do available space and energy resources impact energy efficiency?
    – user74934
    Nov 16 at 17:23
  • I simply mean (a) is your kitchen space better suited to place a pot on a stove top, or on a countertop near an electrical outlet, and (b) in the area where you are located, is the fuel for your stove more or less costly than your electricity. These things might be negligible. In either case, a pressure cooker will cook your beans far more quickly (whether you use a presoak or not) than any other method.
    – moscafj
    Nov 16 at 17:49
  • OK thanks, but please note I am exclusively interested in energy use. Cooking time or cost are not a factor.
    – user74934
    Nov 16 at 17:51
  • Less cooking time = less energy used...No? But if this is strictly a thought exercise....solar cooker?
    – moscafj
    Nov 16 at 17:51
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    A slow cooker is going to be more efficient than prolonged boiling, despite taking longer, so quicker doesn't necessarily mean lower energy. Kidney beans complicate things as they need a hard boil anyway to not be toxic, and slow cookers have a lot of thermal mass to heat up however little you cook in them.
    – Chris H
    Nov 16 at 20:08

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