what do you use for heat

Natural gas hot water radiant floor heat.
I put it in a few years ago and it is the best heat I have ever had.
Set at 62, the 1st floor is 70 right now and it is about 10 outside.
It is very efficient and low cost to operate.
As it was once explained to me, it heats mass (the floor, the couch, the cabinets, etc) and once that is heated it takes less to keep it there- plus when you walk around the house the hot air is not in your face, it is at your feet= no shoes required on the coldest days.
It is great for playing on the floor with my 3 year old too.

Some one mentioned on-demand water heaters, and many issues.
I have one and it is assume. My monthly bill dropped about $75+.
I have heard many units have issues. Mine is a Rinnai and no problemos.