A wood stove, if you can swing it where you are.
A small coal stove and some bags of coal might make a difference.
A kerosene heater is cost-prohibitive, since they raised the price of kerosene, and cr@pped up the fuel to the point it destroys $15 wicks very quickly.
I live in an apartment, so a wood stove is out of the question. I used a kerosene heater years ago when Carter was in office. Wouldn't bother with one now that I'm almost 75. Wouldn't be able to lug the jugs of kerosene up the stairs here. If I freeze to death this winter, my two sons are the beneficiaries on my insurance policy, that is, unless they freeze to death too.
I went all last winter with no NG heat....just to see if I could do it. I did it....so it’s doable.