I know somebody has already suggested it. But go with the heated mattress pad..
I lived in a 1963 double wide for 7 years. The furnace quit the first year, and since
I was paying literal chump change for rent, I tried not to bother the land lord..
I went 3 or 4 years with no furnace.. (it was a $9.95 thermocouple)
The place was cool.. Right next to an old 1870's fort. Ruins right outside my front door.
Old busted pottery and glass all over my front yard.. My land lords had an entire wall
devoted to the things they found.. Old guns (minus the wood), cannon balls, bottles, a
button that was multiple times better than what the museum over at the ruins had.. And what I
though was the coolest one. A key chain, with 14 keys on it. Old school..
Anyways.. The trailer was a piece of shit, even though it was a double wide.. 2x2 walls, all
the insulation had fallen down and was only in the bottom foot or so.. The windows were
those flappy louver things that didn't seal for shit.. In the winter it was a space heater
in the living room, that I sat almost literally on top of, and the heated mattress pad..
I've used electric blankets before.. Mehhh.. But the mattress pad.. It puts like a dome of
warm around your bed.. Even when it got down into the 40's in that trailer, or even the high
30's (and that's as cold as I saw it).. I slept like a baby.. Nice and warm in my little bubble
of warmth. Your foot sticks out of the blanket.. Still warm.. Your nose doesn't get cold. Heat
is coming up through the pillow.. Heated mattress pad all the way..
Even when I did fix the furnace, I only used it when I had company. The heat left as fast as
the furnace could make it.. Cheaper to use the one space heater, and sit on top of it, and use
the heated mattress pad to sleep.
Piece of pottery I found in my front yard.