The type cover is not draining power and your pc is not waking to update. Sleep (as opposed to hibernate) is a low power standby mode, but still uses power in order to hold the RAM in a steady state and allow quick wake up. 7-10% is pretty good overnightYeah, I've noticed my battery drops about 7-10% if I leave it in sleep mode overnight. I started powering it off at night. I wonder if it's Windows update going out to check or something like that. Would be good to find out what is causing the drain. I did leave the type cover attached but I wouldn't think that would draw any power.
Maybe a higher capacity battery?I set my surface to go on hibernate when I press the power button. It's true it doesn't take any power at all but instead of waking instantly it will take 2-4 seconds. I was using an Acer W700 in the last few days and I can say that when you put it to sleep, it barely drains any power even over night, and can wake up in a split second. I wonder how they were able to do it. Acer claims the W700 has something like a 2 week standby time.