are one of those 'lost technologies' that have been nearly forgotten. The amount of fuel to cook foods in a pressure cooker is just a fraction of what you use on the stovetop. Once the pressure rises, the cooker will cook foods up to 3 times faster that ordinarily. Bring it up to pressure, and then turn it off. After the pressure drops (15 minutes or so), then just turn on the burner until it gets pressure again. Also, some have suggested the cooker be put into an insulating box. Probably cardboard will work. This insulation will slow down heat loss and allow you to keep the pressure up longer, and use less fuel. Be careful when using a pressure cooker. My dad reportedly tried making Grappa many years ago, and eventually the cooker exploded making a mess of the kitchen ceiling. We moved shortly thereafter. Inspect your cooker before using and make sure the vents are not clogged. When cooking beans, etc. pour a tablespoon of oil into the water, this prevents the husks from jumping around and clogging the vent. Also, cooker manufacturers recommend not filling your cooker more than half full. It is a good idea to oil the rubber sealing ring before each use. This makes it easier to open the top, and helps proved a better seal. What a great investment if you do any serious cooking. Also pressure cookers can be used with parabolic solar cookers, and possibly with box cookers, but this still requires a little more experimentation and testing.