Fuel
Not all fuels are equal, even if they are classified as the same. This is especially true when it comes to naturally sourced fuels. There are efficiency differences such as the amount of BTU’s emitted, length of burn time, and the amount of smoke or soot. Just as you can make a less efficient stove heat better by using a quality fuel, you can also make an efficient stove produce less heat with cheap fuel. The Ideal situation is an efficient stove burning quality fuel.