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Low Flow Fixture Savings Calculator
Low-flow toilets, aerators, and showerheads cut water usage 25-40% with fast payback.
Net annual savings
$39,146
Payback months
11.5
Net upfront cost
$37,500
How the math works
Annual savings = units × gallons/day × 365 × rate/kgal. Net upfront = cost × units − rebate × units.
150 × 65 × 365 / 1000 × $11 = $39,126/yr savings. Net $37,500 − $15k = $22.5k. Payback 6.9 mo.
How to Use
- Enter number of units.
- Enter fixture retrofit cost per unit.
- Enter gallons saved per unit per day.
- Enter water + sewer rate per kgal.
- Enter rebate per unit.
- Read net annual savings + payback.
Frequently Asked Questions
Low-flow fixture standards?
Toilets: 1.28 GPF WaterSense (HET) vs 1.6 GPF standard vs 3.5-5 GPF legacy. Showerheads: 1.5 GPM WaterSense vs 2.5 GPM standard. Faucet aerators: 0.5-1.5 GPM WaterSense vs 2.2 GPM standard. Dishwashers: 3.5 gallons/cycle Energy Star vs 6-10 legacy. Washing machines: 15-25 gallons/load Energy Star vs 35-50 legacy. Retrofit package per unit: $150-600.
Typical water savings?
Multifamily retrofit (toilet + showerhead + aerators): 25-40% water reduction. Per-unit savings: 15,000-35,000 gallons/year. At $8-14 per kgallon (water + sewer combined): $120-500/unit/year savings. 100-unit building: $12-50k annual savings. Hotel retrofit: 30-50% (higher baseline use). Laundry efficiency: additional 10-20% savings. Multi-billion dollar annual savings opportunity nationally.
Rebate programs?
Most US water utilities offer $50-300/unit rebates for WaterSense toilets. California water agencies: up to $300/toilet. Denver Water: $75-100. NYC DEP: $100-150/toilet, $50/showerhead. Texas munis: $50-150. Stacked with federal tax deductions 179D: 179D deduction $0.50-5/sqft applies to water-efficient retrofits if part of LEED/Energy Star pathway. Project costs often fully offset by rebates + short payback.
Submetering synergy?
Submetering transfers water cost to tenant: tenant then has conservation incentive. Landlord installs submeter + low-flow fixtures simultaneously. Tenant pays reduced water bills. Landlord captures rent premium or eliminates utility loss. Combined retrofit ROI: 2-4 years typical. Huge in Arizona, Texas, California where water is expensive. Utility RUBS (ratio billing): passes water cost to tenants on unit count basis, less precise.
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