BTU, is the abbreviation for British Thermal Unit, which is a measure of energy. For a grill, it’s the total amount of heat output, by all the burners per hour. This is typically measured by the fuel consumption of the burners. Propane has a BTU rating of 21,600 BTUs per pound.
Char-Broil grills don’t generally need as high of an output of BTU’s, because most are equipped with Infrared cooking systems. For a standard grill, you’ll want to look at a BTU rating of 80 to 100 BTUs per square inch. For an infrared grill, you’ll need around 60 to 80 BTUs.
The higher the BTU’s don’t necessarily mean the better the grill.