To a first approximation
Wednesday, April 28, 2010
1:42 PM
To a first approximation: 
Power requirements for a data center = ∑ (power requirements for servers) * (1 + 1/E). 
So, 
Shutting down servers saves power and air conditioning. 
Powering up servers uses power and air conditioning. 
So, 
only keep what you need running. 