I would NOT recommend a propane heater for inside your home. Carbon Monocide poisoning would be of big concern. You would have to keep a window open about 2 inches to vent the room properly.

A generator would be the best solution, but if you don't already have one, you probably won't be going out and spending big bucks to buy one. If you have a grill with the side attachment, you can boil some water and fill up a few hot water bottles. Put them in the enclosures and the snakes will gravitate towards these to stay warm. You could head out to the store and buy some hand/foot warmers. Put them on the bottom of the enclosure, then cover them with a towel. The towel will hopefull prevent a belly burn and they will last 6 hours or more.

BTW, how did you send this message without electricity.

Good Luck!
Jim Smith