96% AFUE furnace gas required: 80,000,000 ÷ 0.96 = 83,333,333 BTU input = **833 therms/year** - Annual savings: (1,000 - 833) therms × $1.20 = 167 × $1.20 = **$200/year** - Additional cost of 96% vs. 80% AFUE unit: approximately $400–$700 more at installation - Simple payback on efficiency upgrade: