Even with a pure heating fuel such as propane, it is still less expensive to heat with propane than with feed consumption. For example, consider that one litre of propane costs $0.66, and generates 24,024 BTUs, or 6054 kcal. In simple terms, the cost of the propane becomes $0.11 per 1000 kcal. Conversely, a grower feed costing $400 per ton ($0.40 per kg), with 3130 kcal per kg of feed, will cost $0.1278 per 1000 kcal.