Self-tutoring about barbecues: the tutor looks into the BTUs one should hope for.
Apparently, 80 to 100 BTU per square inch is best.
I measured our old one outside, which is very good, but wasted away by the weather. Its grill is 15×26 square inches, or 390 square inches. On the side, a stamp says 40000 BTU – exactly what’s recommended.
Source:Oracle Tutoring by Jack and Diane, Campbell River, BC.