I'm not sure that electric heating blankets are recommended for sleeping on, as opposed to under. You could end up damaging the wiring, possibly leading to a short. If that leads to a fire, you'll be toasty warm for the rest of your life! :-(
I'm not overly concerned about that happening. I believe that was recommended when they first were introduced, but no longer. It's an excellent method of staying warm in freezing temps and a small 250 AH powerstation will run mine all night on low. It'll still work if you're under it and inside the sleeping bag, just not as effective.
