We have Econo Heat panel heaters in all the bedrooms. They are 400W as opposed to the 2000W or more that fan wall heaters and oil column heaters run at. They just use natural convection to gently heat the room. I usually put them on about an hour before the kids go to bed and it warms the room noticeably (even when it is snowing outside). They haven't raised the power bill too much considering I leave them on all night in the kids rooms.

That was probably no use to you lol, but maybe worth looking into if you only need to take the edge off.