Question

To keep your house warm what is the most efficient size of furnace to heat your home

Answer 1

The heat output of furnaces, especially gas furnaces, is typically measured in BTUs (British thermal units). A good rule of thumb for home heating is that you need 25 to 35 BTUs per square foot in the moderate climates that are typical throughout much of California, while you may need up to 45 BTUs per square foot in colder climates.