Since the 1960s my cooking and heating set up in my 32 sq.ft. ice fishing shack has been the simple Sterno box stove with terra cotta pot fueled by charcoal briquettes (pic). Earlier this spring I decided to experiment in the back yard using this in my Forester style tarp set up with a piece of plastic over the front opening. Unscientific results were during two 28*F nights 10 briquettes at 9:M lasted until 2:00PM when I got up for a pee break then put 5 more in and lasted till 6:00am when I refueled it with wood for my morning coffee with the water that was kept from simmer to lukewarm all night sitting in my GSI cup on top. Under tarp temp ranged from 40*to45*F throughout the night making for comfortable under tarp temp and sleeping. No reason same results could not be had with leftover larger camp fire coals in lieu of briquettes. Obviously the clay pot is not a backpacking item but in winter it's not a problem if using a sled for gear and in the off season you could always carry in stash away a pot or two in your most frequented area or site.