Luckily, there are all sorts of low-tech ways to stay warm using less heat.

Not many people can afford an astronomical heat bill and the prices of utilities are only going up from here. We'll need to use other methods for staying warm aside from cranking up the thermostat if we want to stay cozy without going broke.

I've lived in all sorts of houses and worked with different types of heat.
Back when I lived in an inexpensive cabin with wood heat and a million dollar view I learned exactly how drafty and chilly our little house was!  The breeze off the lake also increased the nip in the air.  With an older wood stove as our only source of heat, the rooms more distant from the stove moved from chilly to downright COLD.

Currently, I live in an old house with radiators. It's usually cozy in our moderate climate, but on days when the mercury doesn't rise to double digits, it's pretty darned nippy in here. I've gotten up on mornings when the heat is set at 64 to find the main floor stubbornly resisting warmth and staying at a brisk 57 degrees.

There are different heating solutions for more extreme situations.
When you rent, it isn't feasible to insulate or replace the windows and wood stove with more efficient models. In that situation, you have to work with what you've got. So low-tech methods that don't change the house are ideal.

From a prepping point of view, using less heat allows you to extend your fuel supply. You don't want to use up all your propane or wood during the early stages of a power outage. Low-tech methods will let you ration your fuel while still remaining comfortable.

More extreme situations will call for more extreme measures. Here's an article that talks about how to stay warm during a winter power outage and here is an article by Selco that explains how people stayed warm during a long-term SHTF event.