My 15" Retina MBP lives in clamshell mode, hooked up to a large monitor and a large Wacom touch tablet and I don't need to use the laptop's screen or battery most of the time - merely to unplug and carry it about with me occasionally... That's all working great, except that I'm not sure that I am doing the right thing with power management! I would prefer not to 'shut down' the computer every night if possible. Last night, for instance, I let the computer go to sleep and didn't worry about the green light on the magsafe being on. I know the battery won't keep charging after this green light indicates it's full. However, when I was lying in bed, I suddenly became worried it might use a lot of electricity if I literally leave it that way every night. Like mobile phone power chargers notoriously keep sucking energy even when your phone is not connected to them? So I went up to my studio and switched off the switch by the wall plug, thinking I would just switch it on in the morning and then hit a key or the mouse and wake the Mac up. When I touched the mouse this morning, the Mac did wake up instantly, everything going to plan so far. But then I noticed battery power was down from 100% to 94%. I checked the power settings and see that it's set to "powernap" and also to wake up for wifi.. so realised of course that it did have systematic tasks to carry out while sleeping and that when I cut off the mains it became obliged to use the battery to do them, hence the drop. Mmmm. There are a number of difficulties I have with this. Firstly, I don't want the computer to be doing anything during the night. Second, I don't think it would be good to continually and repetitively use my battery that little bit then top it up. I have therefore switched off powernap and the other nocturnal stuff. Of course, now I am wondering whether the laptop will still do some things when sleeping and still use the battery a little. Would it be better to simply leave that green light on, leave it permanently on mains, even when sleeping, to avoid this nibbling of battery power and not worry about it using a bit of electricity just because it's plugged in - or would it use significant amount of electricity merely because it's plugged in like that and ultimately be better to just shut the computer down and then switch off the wall plug too! Remember: I'm not asking whether night time activity on the MBP uses a lot of power. I know it doesn't. I am asking whether keeping it permanently plugged in overnight uses a lot of electricity. Thoughts would be appreciated and please note I have already read through Apple's issued advice.