The most efficient fuel for cooking depends on the specific circumstances. For indoor cooking, natural gas is often the most efficient option, while outdoor cooking can be more efficient with propane or charcoal. Electric cooking can be efficient but is highly dependent on the electricity source. Cooking with wood can be efficient if using a modern, efficient stove or oven, but traditional wood fires are often less efficient and produce more pollutants. Overall, the most efficient fuel for cooking is one that is matched to the specific situation and equipment being used.