RESNET’s Water Efficiency Rating System HERSH2O®

What is HERSH20®


The Importance of Our Water Resources

Water resources are becoming increasingly strained in many parts of the country and water prices are increasing faster than energy prices. Water price increases are not based solely on the availability of water, but also are significantly impacted by the costs to upgrade aging water infrastructure and water utility rate structures. This means that the potential for water cost savings through water efficiency measures is available in nearly all regions of the U.S.

To address this issue RESNET has created a water efficiency rating system, HERSH2O®.


Builders Can Now Easily Rate the Energy and Water Efficiency of Their Homes

HERSH2O® builds off RESNET’s nationally recognized Home Energy Rating System (HERS®) Index, which is the gold standard for rating the energy efficiency of a home. HERSH2O® is a system for rating whole-house water efficiency that includes both indoor and outdoor uses. With the average family spending more than $1,000 annually on water costs, HERSH2O® provides a simple, easy-to-compare rating on a scale of 0-100+; where lower numbers mean less water use.

Builders that are already having their homes HERS® Rated, can easily add a HERSH2O® Rating.


Use HERSH2O® to Achieve the WaterSense Label for Homes

RESNET is a WaterSense Home Certification Organization (HCO) and HERSH2O® is a WaterSense Approved Certification Methodology. This means builders now have a performance-based approach to achieving the WaterSense label for their homes. By achieving a HERSH2O® score of 70 or less and meeting a few simple requirements, builders can label their homes as WaterSense certified.

Click here to find a RESNET Certified WaterSense Home Verifier.


HERSH2O® is Based on an Accredited National Standard

The basis for HERSH2O® is an ANSI standard known as ANSI/RESNET/ICC 850. The first version of this standard was published in the summer of 2020. The development of this standard is a collaboration between RESNET and the International Code Council.


How is a HERSH2O® Rating determined? What is the Home Being Rated Against?

A HERSH2O® rating is determined by comparing the home that is being rated with a “Reference Home” that is representative of construction practices (plumbing products and practices) circa 2006. There were a number of data sources used to develop the models that provide an estimate for both indoor and outdoor water usage. These data sources include:

  • Residential End Uses of Water Study, 1 and 2
  • 2005 Residential Energy Consumption Survey
  • ANSI/RESNET/ICC 301-2014, Addendum A
  • DOE Technical Support Documents from 2006 NAECA Standards
  • World Water and Climate Atlas

How to become a HERSH20 Rater?


Become a HERSH2O® Rater and a WaterSense Home Verifier

All active certified RESNET Home Energy Raters and Rating Field Inspectors are eligible to conduct HERSH2O® ratings after completing the online HERSH2O® Rater Training. Becoming a WaterSense Home Verifier requires completion of the HERSH2O® Rater Training and viewing the WaterSense Version 2 video on the RESNET training portal.


Become a HERSH2O® Provider

All current RESNET accredited Rating Quality Assurance Providers (QA Provider) are eligible to become HERSH2O® Rating Providers after meeting the following criteria in the Implementation Guidelines for HERSH2O® and WaterSense Version 2 and completing the HERSH2O® Provider Application.

How to become a CalCERTS/RESNET HERSH20 Rater?


Video: RESNET HERS® Raters — Help Lower Water Bills for Homes with HERSH2O®

ANSI/RESNET/ICC Standard 850-2020

Implementation Guidelines for HERSH2O® National Rollout

RESNET Inspection and Verification Guidance for HERSH2O®

HERSH2O® Inspection Checklist

ICC Sustainability Membership Council Video Feature on HERSH2O®

RESTalk Podcast on Introducing the RESNET Water Efficiency Rating System HERSH2O® with Mark Johnson (ICC) and Jacob Atalla (KB Home)

Introducing RESNET HERSH20: RESNET’s Whole House Water Efficiency Rating Infographic