We still heat with primarily wood and a K-1 Toyo direct vent wall mount to keep the temps constant. Low tech works well in a 25' x 30' house with tight windows and plenty of insulation. A couple cords of wood and slightly less than 100 gallons of K-1 kept us comfortable last winter. It will be more this year. The water heater is a Rheem Marathon, a fairly conventional but very well insulated unit. If we lose power we'll still have warm water a couple days later.