From what I have seen advertised, the larger the reflectors, the hotter the pot gets. Also, if the pot is inside a glassed in box, the heat can't escape as easily. However, these ovens are about the size of a suitcase folded up, and are made from metal, and are almost as expensive as a gas or electric range. Like $400-$600. I think those will work, but why not just get a Coleman stove with a box oven and some propane bottles, unless you want this for home use or survival use if fuel cannot be had. If you live in the plains states or desert, firewood might be a problem for you. I think the idea is great, but only after all other survival supplies have been purchased.