Old furnace burned 788 gallons to deliver X BTUs of heat. - New 96% furnace delivers the same X BTUs by burning: 788 × (0.80/0.96) = 656 gallons. - Annual savings in gallons: 788 - 656 = 132 gallons. - At $2.88/gallon (2025 price): 132 × $2.88 = **$380/year savings from the new furnace vs. old furna