Link one TechRepublik's 3 page spread article on this subject says large savings available per computer - of hundreds of pounds per annum (based on 16hrs/24hr day being in standby.....and able to be awoken easily by fax, routine automated maint etc).
Hibernation is a total saving because you can power off completely and still resume at the same point.
They cite US$177 (left on continuously) versus US$27p.a. in standby (keyboard, modem, PCAnyWhere or fax wakeable).
Link two = Microsoft White Paper on the subject.
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