County DWS adds webpage with new water-use calculation method

The County of Maui Department of Water Supply (DWS) launched an additional webpage to provide the public with information on the new method for calculating water use for water service requests, effective Jan. 1, 2026.

The new webpage — www.mauicounty.gov/2895/Water-Use-Calculation-Method — includes a Water Use Submittal Checklist, guidance on the new Equivalent Single Dwelling (ESD) method and an online calculator to help estimate a property’s water demand. It also provides standard meter size information to help applicants determine the right meter for their water needs.

The update follows the Maui County Council’s adoption of Ordinance 5759, which directs the department to base an individual property’s domestic water demand and development impact fees on projected daily water use rather than counting individual water fixtures.

This new method applies to building permit applications and requests for new or additional water service submitted on or after Jan. 1, 2026. Applications submitted before that date are not affected.

Additional frequently asked questions with answers include the following:  

Q: What is an Equivalent Single Dwelling (ESD)?

A: An ESD is a standard unit of measurement equal to 300 gallons per day.

Q: How is water use calculated under the new method?

A: Water demand is calculated using the ESD formula. The updated website includes the equation, pre-calculated values for common home types, an online ESD calculator and a Water Use Submittal Checklist to help you submit your information.

Q: Does this change affect my current water bill?

A: No. This update changes how water use is calculated for new building permits or additional water service requests. It does not affect existing accounts or previously submitted applications.

Q: When did this new method take effect?

A: Jan. 1, 2026.

Q: Who does this apply to?

A: Homeowners, developers, and anyone applying for new building permits or requests for new or additional water service. The method also provides guidance for nonresidential properties.

Q: Are Lahaina residents rebuilding affected by this new methodology?

A: Yes, Lahaina residents rebuilding in the burn zone will use this new methodology.

Q: Where can I find more information?

A: Visit the Department of Water Supply’s webpage:  www.mauicounty.gov/2895/Water-Use-Calculation-Method