“will a heat exchange pot be more efficient than taking that extra weight in a decent windscreen?”
A decent windscreen can be very light. Â While I’ve made UL HX fins in my garage and attached them to SUL “pots”, commercially available HX pots are considerably heavier than the lightest non-HX pots.
And there are weather conditions in which you NEED a windscreen to get any cooking done.
So first, have a good windscreen.
“Thinking (of) big groups using pots to a full US Gallon or bigger or for dedicated snow melting use for medium sized parties in really cold weather”
Then, yes, HX pots can save you much more fuel weight than they add in pot weight. Â I do a fair number of group (4 to 10 people) trips in winter here in Alaska. Â Even using 32F water, a large HX pot (I have many) lets you cook group meals more easily, and lets everyone have more tea, coffee and hot chocolate for whatever amount of fuel you’ve brought. Â More boiled water means less treated (filter, UV, chemical) water. Â When you have to use snow or ice (sometimes the lakes freeze 18+ inches thick and chainsaws weigh A LOT), then HX pots come ahead even sooner.
Here’s one perspective: If I’m packing for a multi-night family trip, I’m bringing an HX pot (another 3-5 ounces versus a non-HX pot) or one more 220-gram canister (357 grams with metal = 13 ounces).
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