I spent a week in a traditional Japanese apartment in January. There was an electric heat pump for heating and cooling, backed up with a portable kerosene heater. The only heated water was a gas in-line demand heater in the kitchen. The bath tub had its own gas heater. There didn't seem to be any insulation, there, so keeping warm in your own place was interesting.
You got the most heat from an electric heater under the short little table shrouded with blankets -- the kotatsu? That was cozy!