We use an electric blanket and have several blankets we could put on top of it if we had to. We do not have the furnace on at night but we like to sleep in a cold bedroom well covered up.
When camping in a tent without electricity in below freezing temperatures we have used sleeping bags that zip together, flannel sheets sewn to make a sleeping bag that is partly open down one side and if necessary blankets to throw on top of the sleeping bags.
If you are cold at night you can use a heavy cotton sweat suit to sleep in plus socks.