# How the WaterSense Calculator Works

The WaterSense calculator requires users to provide basic information about the household fixtures (faucets and/or toilets) that are being installed or replaced with WaterSense labeled models. Based on the number of people expected to use the fixtures in each household and other simple inputs, the calculator provides estimates of the amount of water and energy that you can expect to save by installing WaterSense labeled products. Expected dollar savings are also provided.

Javascript must be enabled to use the calculator. A Microsoft Excel version is also available if Javascript is disabled for your Internet browser.

### On this page:

- Required Inputs
- Results
- Assumptions
- Excel version of the calculator
- Finding WaterSense labeled products

## Required Inputs

### Number of households:

If you are installing WaterSense labeled products for your home, enter "1". If you are installing WaterSense labeled products in an entire apartment building, for example, enter the number of apartments that are receiving the WaterSense labeled products. If you would like to estimate the amount of water or energy that could be saved if an entire community or city installed WaterSense labeled products, enter the number of households up to 999,999,999 (without commas).

### Number of people living in each household:

You may select the number of people living in each household up to 10. If you do not know the number of people living in a household, or you are performing estimates for an entire community, we suggest that you select 2.6, which is the national average.

### WaterSense labeled products being installed:

You may choose WaterSense labeled faucets, WaterSense labeled toilets, or both.

### How your water is heated:

If you are installing WaterSense labeled faucets, or retrofitting old faucets with WaterSense labeled aerators, you must select either natural gas or electricity as the method by which your water is heated. This allows the calculator to provide an estimate of the energy savings that may be realized by installing WaterSense labeled fixtures. If you do not know how your water is heated, you may select "don't know". However, if "don't know" is selected, the calculator will not be able to provide an estimate for energy savings and will only provide an estimate of the amount of water that you can expect to save.

If you do not know how your water is heated, check your energy utility bill, or contact your energy provider or your landlord to determine if natural gas or electricity is used to heat your water.

### When were the existing toilets installed:

If you are replacing toilets, you must select an installation year for the old toilets: before 1980, between 1980 and 1994, after 1994, or "don't know". This allows the calculator to provide an estimate of the water savings that may be realized by installing WaterSense labeled toilets. Older toilets use more gallons per flush that toilets installed in recent years. If you do not know when your toilets were installed, select "don't know" and the calculator will provide an estimate based on 3.5 gallons per flush for the old fixtures.

Alternatively, if you are purchasing a new toilet, for example as part of new construction, select "not replacing (installing new)". This allows the calculator to estimate the savings that may be realized from the purchase of WaterSense labeled toilets over non-WaterSense labeled toilets for new installations.

### Length of time for savings estimates:

The calculator will generate estimated water and energy savings based on various lengths of time. You may generate the estimated savings that you may expect to realize by using WaterSense labeled products for a single day, a week, a month, or a year.

After entering all of the inputs, click the calculate button. If you have failed to answer all of the questions, you will be prompted to do so.

## Results

Estimates for expected water savings and energy savings are provided. Note that ** energy savings are only realized if faucets are being replaced**, since faucets usually use warm water which requires electricity or natural gas to heat. Water savings are a combination of the savings expected from both water and sewer/wastewater utility bills.

You may change the input variables to calculate new results based on different scenarios.

**Please note that actual savings may vary from those predicted by the calculator. Users should focus on the relative savings of various scenarios, rather than the absolute savings.*

cu ft = cubic feet

KWh = kilowatts per hour

## Assumptions

To provide estimated water and energy savings, the calculator assumes that all fixtures (e.g., faucets and/or toilets) within the household are being replaced or retrofitted with WaterSense labeled products.

It is assumed that the cost of a kilogallon of water (1,000 gallons) is $6.06 based on national averages.

### To estimate gallons of water saved for toilet installations:

The calculator determines the difference in gallons used by a WaterSense labeled toilet versus the toilet being replaced. WaterSense labeled toilets use 1.28 gallons of water per flush or less. It is assumed that toilets installed before 1980 use about 5 gallons per flush. Toilets installed between 1980 and 1994 use about 3.5 gallons per flush, and toilets installed after 1994 use about 1.6 gallons per flush. The calculator then multiplies the savings by the number of households, the number of people in each household, and the time period specified by the user. The calculator also assumes an average of 5.05 flushes per person per day.

### To estimate gallons of water saved for faucet installations:

The calculator determines the difference in gallons used by a WaterSense labeled faucet (or the retrofit of an old faucet with a WaterSense labeled aerator) versus the faucet being replaced. It is assumed that installation of a WaterSense labeled faucet, or the retrofit of an old faucet with a WaterSense labeled aerator, results in a savings of about 0.6 gallons per person per day. The calculator then multiplies the savings by the number of households, the number of people in each household, and the time period specified by the user.

### To estimate energy savings associated with the installation of WaterSense labeled faucets, or the retrofit of old faucets with a WaterSense labeled aerators:

The calculator determines how much it would cost to heat the water saved based on the selected energy source (e.g., natural gas or electricity). It is assumed that 73 percent of water that comes out of the tap in a typical household is heated. It is also assumed that the average cost of 1 cubic foot (cu ft) of natural gas is $0.013 and that the average cost of 1 kilowatt-hour (kWh) of electricity is $0.104 based on national averages.

## Excel Version of the WaterSense Calculator

A Microsoft Excel version of the WaterSense calculator is also available for users that do not have Javascript enabled for their Internet browser. To use the Excel version of the calculator, click on the link "MS Excel version" in the upper right-hand corner on the calculator screen. You will be prompted to open or save the file. By selecting open, a new window will appear in your browser and you may enter your inputs and generate expected water and energy savings. Alternatively, you may save and download the Excel file to your hard drive if you prefer.

- Excel version of WaterSense Calculator: WS-watersense-calculator.xls(1 pg, 39 K)

To use the Excel version of the calculator, you must provide the inputs for questions 1–4 as follows:

- Number of Households: type the number of households in cell B5.
- Number of People in Household: select from the pull-down menu in cell B6.
- Time Frame: select from the pull-down menu in cell B7.
- Products: select from the pull-down menu in cell B8. You may choose faucets, toilets, or faucets and toilets.

After selecting the fixtures to be installed, you will be asked follow-up questions in cells B7 and/or B8 for how your water is heated (if faucets is selected) and the age of the toilet being replaced or installed (if toilets is selected).

You may also reveal the details of the calculations by unprotecting all of the cells in the Excel spreadsheet. To do this in Excel, choose: Tools / Protection / Unprotect Sheet. Then, select the entire spreadsheet (by clicking the box in the upper left corner that joins the column and row labels). After selecting the entire spreadsheet, reveal the hidden rows by choosing: Format / Row / Unhide.

## Finding WaterSense Labeled Products

When you use products bearing the WaterSense label, you can expect exceptional performance, savings on your water bills, and assurance that you are saving water for future generations. Look for the WaterSense label when buying plumbing fixtures.

Only products that are independently tested to meet EPA criteria for water efficiency and performance carry the WaterSense label.