Brewhouse efficiency is a crucial factor in beer brewing as it reflects the skill and equipment of the brewer. It plays a role in adjusting the total points to get accurate results for OG, FG, and ABV calculations. For instance, if you have a total of 310 points from your grain bill, and you're working with an average efficiency of 75%, you would adjust the points to 232.5 (310 points * 75% efficiency).