Laundry with Harvested Rainwater in Hawaii

Using harvested rainwater for laundry in Hawaii is a practical way to reduce your water bill and conserve municipal supplies. With 63.7 inches of average annual rainfall, a 1,500-square-foot asphalt shingle roof in Hawaii can collect approximately 45,229 gal per year. laundry requires roughly 15 gallons per day per person, year-round. With this setup, rainwater can meet approximately 100.0% of your laundry needs, saving an estimated $164.25 per year.

Annual Harvest 45,229 gal 1,500 sq ft roof
Annual Demand 10,950 gal laundry (2 people)
Demand Met 100.0% of laundry
Rec. Tank 5,000 gal storage capacity

Monthly Supply vs. Demand for Laundry in Hawaii

The table below shows how your monthly rainwater harvest compares to laundry demand throughout the year. Green values indicate months where your harvest exceeds demand (surplus water for tank storage), while red values show months where you will draw down your stored reserves. Laundry is a year-round use, so demand remains constant regardless of season. Tank sizing should bridge the gap during your driest months.

Month Harvest (gal) Demand (gal) Balance
January 3,738 930 +2,808
February 3,140 840 +2,300
March 4,486 930 +3,556
April 4,112 900 +3,212
May 2,841 930 +1,911
June 2,392 900 +1,492
July 3,364 930 +2,434
August 3,588 930 +2,658
September 3,738 900 +2,838
October 4,336 930 +3,406
November 4,859 900 +3,959
December 4,635 930 +3,705

Harvest by Roof Size for Laundry

A larger roof collection area directly increases your harvest and the percentage of laundry demand you can meet with rainwater. The table below shows how different roof sizes perform in Hawaii for laundry (calculated for 2 people).

Roof Area Annual Harvest Demand Met Rec. Tank Savings/Year
1,000 sq ft 30,153 gal 100.0% 2,500 gal $164.25
1,500 sq ft 45,229 gal 100.0% 5,000 gal $164.25
2,000 sq ft 60,307 gal 100.0% 10,000 gal $164.25
2,500 sq ft 75,383 gal 100.0% 10,000 gal $164.25

Setting Up Rainwater Harvesting for Laundry in Hawaii

Using rainwater for laundry in Hawaii offers a unique benefit: rainwater is naturally soft, meaning you can use 30-50% less detergent while achieving the same or better cleaning results. Hard municipal water requires more soap to lather effectively, and mineral deposits can make fabrics stiff and dull over time. A rainwater-fed laundry system requires the same setup as toilet flushing — dedicated non-potable plumbing, a pump-and-pressure system, and sediment plus carbon filtration to remove any debris or tannins that could discolor fabrics. The filtration requirements are slightly higher than for toilet use because you want to protect both your clothing and your washing machine from fine sediment. A first-flush diverter on your collection system is especially important for laundry use to keep water clean.

Metal Roof Upgrade: Laundry in Hawaii

Upgrading to a metal roof increases your collection efficiency from 80% (asphalt shingle) to 95%, boosting your annual harvest to 53,712 gal from a 1,500-square-foot roof. This increases your laundry demand coverage to 100.0% and raises annual savings to $164.25. Metal roofs also last 40-70 years compared to 20-30 years for asphalt shingle, and their smooth surface sheds debris more effectively, reducing maintenance on your collection system and improving water quality.

Other Uses for Rainwater in Hawaii

Explore how harvested rainwater can serve other needs in Hawaii:

Get Your Custom Estimate

Use our Rainwater Harvesting Calculator to enter your exact roof area, material, and combine multiple uses for a comprehensive harvest analysis. See all rainwater harvesting data for Hawaii or compare all 50 states.