The above acronym stands for British Thermal Units, and is a measurement of how much heat can be produced. People get obsessed with getting models with the highest BTUs , but this is a bad idea for a few reasons. First, you aren’t going to be running your burner at maximum heat all the time, because that would increase the rate of breakdown (likewise, you don’t drive at 100mph all the time). Second, an average home requires 4,500-21,000 BTU, so you really don’t need anything higher. Third, BTU numbers can be gamed by the manufacturers by using different types of fuel with higher burn temperatures. That being said, It is more important to consider is consistency of heat output. Will you get a steady flow of heat for 10 hours, or will the fire get really hot for one hour and then not produce as much heat?