I just received an email with this question: "How do you know which calculator to use when trying to figure out the National Average. Your helpful hints indicate to use either calculator C or B. My question is, how do I know which one to use?"
For buildings not covered by Energy Star, teams need to download the USGBC's benchmarking tool (from LEED Online or the Registered Project Tools Page).
Once you download the calculator (both Options are covered in a single Excel file as separate worksheets), there is an tab termed "Eligibility" that walks through which Option you should use. There are also built in error messages that will warn you if you are using the wrong option.
Finally, the USGBC has shuffled the terminology around a bit, such that Option B from 2008 is now called Option 1 in 2009, and Option C from 2008 is now Option 2. And in both cases, they aren't really "Options", because you don't get to choose at will, but rather are required to use the one that matches the situation in your building based on the space types present.