Whatever you do, do NOT bring a 20lb propane tank into any part of your house. That is extremely dangerous.

If necessary, you can run a hose from outside (where your tank is safely stored ).

If you must use propane indoors, the safest solution is to use the small 1 lb bottles. Those are okay to bring indoors.

If you're fortunate enough to have a natural gas fireplace, you can usually use that for heat even if the electricity is off. You won't get the fans blowing hot air into the room, but you'll get enough radiant heat to get by.

Also, FWIW, natural gas hot water heaters often work just fine without electricity.

Good luck!