Rainwater Harvesting in Hawaii

Did you know it’s raining money? Yes, in many parts of the world, liquid gold is falling from the sky! Here on the Hamakua Coast of Hawaii, average annual rainfall has the potential to supply the majority of our water needs. All you need is a sustainable rainwater harvesting or rainwater catchment system to take advantage of it. 

What is a Sustainable Rainwater Harvesting System?

Quite simply, a rainwater harvesting system is a technology that collects and stores rainwater for human use. There are many different types of systems, ranging from simple to complex. 

The Office of Energy Efficiency and Renewable Energy gives a good overview of the main components of a rainwater harvesting system here. A typical catchment system uses a roof surface of a home to capture rainwater, a piping system, a filter, a pump, and a cistern to collect it. Systems that are designed to include potable water use are more complex, requiring additional water treatment and sanitation. 

The College of Tropical Agriculture at the University of Hawaii has a helpful guide to rainwater harvesting. The 50-page report covers everything from building materials and components to water storage, system maintenance, common problems, to water treatment and testing.

The Benefits of Rainwater Harvesting 

The benefits of using a sustainable rainwater harvesting system for home water use are numerous.

  • Save money
  • High ROI
  • Be more independent and self sufficient 
  • Control over water quality 
  • Reduce environmental footprint 

Average Cost of a Rainwater Catchment System  

Rainwater catchment systems are an extremely affordable green energy technology. The average cost of installing a typical system on a single family home in the United States is $2,500. Costs typically range between $1,000 – $5,000 for a roof top collection rainwater harvesting system. Check out this Maui family’s tiny home blog on setting up their own rainwater catchment tank.

How to Calculate the Output of Your Rainwater Catchment System Based on Roof Square Footage 

To calculate how much rainwater you have the potential to capture from your roof, you’ll need to know:

  1. The square footage of your roof
  2. The average annual inches of rainfall in your area 
  3. Multiply the roof size by 0.56 to find the number of gallons generated from one inch of rainfall (assumes 90% efficiency) source: greywateraction.org 

Let’s say that you have a 1,600 square foot roof and you get 65 inches of rainfall annually.

1,600 x .56 = 896 gallons per inch of rainfall 

896 x 65 = 58,240 gallons of water a year

That is a decent amount of free water! But how does that compare to average water usage? Let’s take a look at average water consumption in the U.S.

Water Consumption in the U.S.

According to the EPA, the average American household uses 300 gallons of water per day. That’s 5 swimming pools of water (over 100,000 gallons) a year! 70% is used indoors and 30% is used outdoors.

You can see that rainwater catchment has the potential to supply a large percentage of a typical household’s water needs. Simply replacing all your outdoor water use with rainwater catchment can cut your water bill by 30%. 

Rainwater Harvesting and Sustainable Water Systems at Kuwili Lani 

At Kuwili Lani, we get ample rainfall year round. Average rainfall is 65-75 inches annually. This makes our location prime for rainwater catchment systems. Kuwili Lani community members have the creative freedom to decide how they want to design and implement their own water system. 

In addition, residents have access to our private municipal water system. Our water system is solar powered. Most residents choose to incorporate a mix of municipal water for indoor use with a rainwater harvesting system for outdoor use. For those that want to be totally independent, there’s the option to add a water treatment system for potable water.

Our Partners 

If you’re considering installing a rainwater harvesting system on your property, it’s important to work with a trusted company. We are proud to partner with local rainwater catchment companies in Hawaii.

Have more questions about rainwater harvesting? Contact Us!