I may have found a solution from another thread. I'm fairly new to macs, but I also have a problem, however mine seems to have it only on occasions, somedays would loose 1-3 % overnight, and others would loose 50%. I found a thread that said to type the terminal command pmset -g assertions. Below is my read out. It shows that there is 1 app preventing idle sleep; BOOM. I realize that UserIdlesleepmode is not the same as Sleep Mode, but you might find something is preventing your computer from sleeping properly. When I quite BOOM (An Audio boosting program), The PreventUserIdleSystemSleep went to zero when i re-run the pmset - g assertions command. Some users are reporting that spotify was the culprit, and others say itunes was a problem. I'm testing the solution now. https://discussions.apple.com/thread/3349374?answerId=16238880022#16238880022
ComputerName:~ LoginName$ pmset -g assertions
3/2/14, 8:45:01 AM PST
Assertion status system-wide:
BackgroundTask 0
PreventDiskIdle 0
ApplePushServiceTask 0
UserIsActive 1
PreventUserIdleDisplaySleep 0
InteractivePushServiceTask 0
PreventSystemSleep 0
ExternalMedia 0
PreventUserIdleSystemSleep 1
NetworkClientActive 0
Listed by owning process:
pid 413(coreaudiod): [0x00000001000019e2] 00:00:06 NoIdleSleepAssertion named: "com.apple.audio.'AppleHDAEngineOutput:1B,0,1,1:0'.noidlesleep"
pid 413(coreaudiod): [0x00000001000019d7] 00:02:07 NoIdleSleepAssertion named: "com.apple.audio.'BoomEngine:0'.noidlesleep"
pid 65(hidd): [0x0000000a00001939] 00:54:59 UserIsActive named: "com.apple.iohideventsystem.queue.tickle"
Timeout will fire in 855 secs Action=TimeoutActionRelease
Kernel Assertions: 0x108=BT-HID,MAGICWAKE
id=503 level=255 0x100=MAGICWAKE mod=3/2/14, 8:07 AM description=en0 owner=en0