20 SEER unit: 24,000,000 ÷ 20,000 = 1,200 kWh × $0.13 = **$156/year** - Annual savings from higher efficiency: $84/year - Added cost of 20 SEER vs. 13 SEER unit: approximately $700–$1,200 - Simple payback: $950 ÷ $84 = **11.3 years**