Old verses new with big savings

Just look at the difference in size between the old furnace and the new furnace. Physically the new one is one quarter the size of the old one. Heat output at 100,000 BTU, the new one is just over half the size of the big brute. The new furnace has a blower and the heated air is forced through the ducts bringing heat to the furthest extremities of the home within minutes. The old gravity furnace had no blower and worked on the theory that hot air rises, and it did, slowly and inefficiently.
The old heating system required massive amounts of heat to keep the house warm because the was no insulation in the attic or walls and the original windows were un-insulated with single pain glass. Adding insulation and better windows meant that this house was able to reduce their heating bill substantially.