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Water Use Coefficient
Water use coefficient


What does coefficient mean?

Because water efficiency is required to win this contest, properties must meet a minimum water efficiency level to be judged. The H2Ownit Landscape Awards require all eligible properties to have a Water Use Coefficient of less than 11.2 gal/sq ft.

To calculate your property's Water Use Coefficient you'll need two pieces of information; your Outdoor Use Estimate and your Outdoor Area Estimate. We've included examples below to help you compute both of these numbers. Customers are encouraged to evaluate their property’s water efficiency prior to application. Properties that are ruled ineligible cannot be re-submitted for a full year after they fail the eligibility test.



How to determine your Water Use Coefficient: 
There are several steps involved in calculating your Water Use Coefficient and they are outlined for you here. Don't worry if it seems like a lot, we'll walk you through each step below!

Determine Total Water Usage

Add up all water usage for 12-month period being evaluated

Determine Outdoor Use Estimate
Subtract estimate for indoor water usage from Total Water Usage

Determine Outdoor Area Estimate
Subtract the Livable Square Footage from the Lot Square Footage

Compute Water Use Coefficient
Divide Outdoor Use Estimate by the Outdoor Area Estimate





The first step in calculating your Water Use Coefficient is to determine your Total Water Usage, which is the sum all your water usage for the 12-month period being evaluated.

You can do this by adding up the usage on all 12 of your last bills, or use the Pay or View Your Utility Bill function through the City's web site to view your usage online: 



Log in using your account number (If this is your first time logging in, you will need to begin by registering your account)

Log in



Once the basic account information pops up, select Consumption from the purple menu on left.

Consumption


Click on the water meter number to see charts with water usage for recent years.

Water Meter


Add up your water usage from the last 12 months to get your Total Water Usage. Note that water usage is shown in thousands of gallons.
For this example, the Total Water Usage is 101,000 gallons.

Sum of Water Usage



Use the Total Water Usage to compute your Outdoor Use Estimate:

 
Our goal is to determine an estimate for outdoor water usage, so we have to subtract an average estimate for indoor water usage. For this contest, households are assumed to be efficient both indoors and out. The Average Efficient Indoor Water Use (based on an average household size of 2.51 residents) is assumed to be 35,000 gallons.



Next, subtract the Average Efficient Indoor Water Use of 35,000 gallons from your property's Total Water Usage

In this example, the household used 101,000 gallons in 12 months, making the Outdoor Use Estimate 66,000 gallons:

Total Water Usage                           101,000 gallons
Average Efficient Indoor Water Use    35,000 gallons
Outdoor Use Estimate                        66,000 gallons




Determining your Outdoor Use Estimate is the first half of the equation. Next, use the Maricopa County Assessor’s Residential Property webpage, along with our example page to help you determine your Outdoor Area Estimate. Once you've done that, continue on below.




Now that you have your Outdoor Use Estimate and your Outdoor Area Estimate, you're ready to calculate the Water Use Coefficient for your property.


Using our example numbers, divide the Outdoor Use Estimate for the past 12 months by the Outdoor Area Estimate to determine the number of gallons used per square foot:


 66,000 gallons / 4,710 sq ft = 14.01 gal/sq ft.
 

14.01 gal/sq ft is greater than 11.2 gal/sq ft.  So this sample property is not efficient enough in its water use to be eligible for the contest.


If however, only 86,000 total gallons of water had been used here, the Outdoor Use Estimate would have been 51,000 gallons.

51,000 gal / 4,710 sq ft = 10.8 gal/ sq ft.

With a Water Use Coefficient of 10.8, the property would be eligible for the H2Ownit Landscape Awards.




 


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City of Goodyear • 190 N. Litchfield Road • Goodyear AZ 85338 • Phone 623-932-3910 • Toll-Free 1-800-872-1749
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