In our company IT yearly general status report I found a part saying that the company has almost 13,000 Computers (80% XP and 20% other) located in different branches.
According to this report, approximately 50%
Of the users are leaving their PC on during the week and this cost the company $150,000 yearly.

Actually, I do not know how they calculated it. Any idea about the way how usually calculates such thing and about the accuracy of this money amount (150,000) will be appreciated.

Thank you.