This instance less is more.
Here is one way I can think of that would allow someone to use something like off grid PV for a useable amount of heat and actually stay nice and warm.
I have had this large double bed heater for a few years now. The kill-a-watt meter tells me that if I keep both sides cranked up on high all night it uses about 0.1kwh.
Could use even less than that if one were to only use 1 side, or a small bed heater coupled with a lower setting.
A small space heater can use that much power in about 6 minutes.
Its nice and toasty. The area immediately around the heating wires is over 90'F. Put this only under a sheet the effect is pretty much instantaneous. If its under one of those foam pad things, turn it on an hour or 2 before bed.
No I did not make this. I bought if from wall mart for $70 in 2006 if I remember correctly.
Well worth it.