Sounds good. If you don't feel like waiting to find out, it's not hard to estimate your relative costs between electricity and propane, if you can rustle up electricity and propane costs in your area plus a bit of info on your propane heating equipment.
If you're going to be running inexpensive electric heaters while you sleep try to be really careful about fire -- electric heat is inherently safe but small heaters can get really *hot* and be a fire risk if they're near anything flammable. Easiest thing to do is to pick up a couple of loose ceramic tiles next time you're in a home improvement store -- they're a buck or less in an ugly pattern, totally fireproof and pretty good insulators to boot. Try to find 18x18 tiles if you can.
I'll just pass on the following advice from my parents :
"If you're cold why don't you put on a sweater and some thick socks ?"
