Is 5% battery loss per 8 hours of non-use normal?

No, I leave mine fully charged in the evening (not switched off), and it still shows 100% in the morning.
I tried Skype but I quickly gave up because of that drain problem.
No wi-fi, no Skype or anything else then.
Bluetooth has never worked anyway...

Jacques

You may have something still running in the background. Looking in settings will tell you how much usage you have in 8 hours.

Seems excellent to me. Do you expect the iphone to run on zero battery power?

I'd say yes too having wifi on mean that it will keep the connection
open and if the connection is weak it may be searching for stronger wifi connections

also unless you use flight mode it will also keep the connection with your gsm tower
and if that connection is weak it will be searching for stronger towers

Wifi doesn't stay connected when your phone goes to sleep, so your phone will be on 3G and may use battery searching for signal.

I think I lose close to that amount overnight.

When I was running 4.0, after a full charge it would show 100% after 8-9 hours overnight. Since 4.1 and 4.2 I lose around 5% overnight. When it is around 50%, it seems I lose a little more. My thoughts are that 4.0 had a different battery reading with 4.2 being more accurate. I have no battery issues and get just shy of 3 days with 5-6 hours of internet and calls.

To the original poster: I wouldn't worry about that. It can be good to reset data just before bed and see how much has been used overnight. If you clicked yes to helping Apple when you loaded up the phone- chunks of data could be taken from your phone and decreasing battery life while you sleep.