Should my energy collectors be running even when I'm logged off?
Solution 1:
The server will by default keep a certain number of chunks near the server spawn loaded at all times, regardless of people logged in or actual chunk loaders. To my knowledge there's no way to disable this at all in Minecraft 1.2.5.
Solution 2:
128 blocks out in any directions from spawn is loaded. when you arent on the server. you can change this in the server properties. ;D