Replacing a 3.5 GPF pre-1994 toilet with a 1.28 GPF HET: - Savings: 2.22 gallons per flush - At 5 flushes/day per person, 4-person household: 16,206 gallons/year saved - At $0.01/gallon average water+sewer rate: ~$162/year savings - Toilet cost: $200–$400 → payback: 1–3 years