Water-Energy Toolkit: Understanding the Carbon Footprint of Your Water Use

For a complete description of available tools, download: Water-Energy Toolkit: Understanding the Carbon Footprint of Your Water

Saving water saves energy. But how much? While businesses and homes that use water will ultimately pay for the energy needed to pump and treat water through their water and sewer bills, few realize that these energy costs are typically on the order of 30%-60% of a city’s entire energy bill. Even more energy is used inside our homes and businesses to heat and cool water, but again, few people realize just how much energy is associated with their water use. For instance, did you know that water heating alone is typically the second or third largest energy expenditure in American homes?

River Network's 'Simple' Water-Energy Calculators

River Network has developed a series of “simple” calculators and tools to help you find out how—and how much—we can reduce our carbon footprint through water efficiency. These tools were produced to explore assorted aspects of the energy and carbon emissions embedded in different types of water supplies. The five interactive, Microsoft Excel-based tools developed by River Network are:

For step-by-step instructions on how to estimate the energy intensity of your water supply and wastewater treatment systems download:

Over the past few years, a number of useful tools have been developed by other organizations seeking to increase awareness of the energy and greenhouse gas emissions associated with water use and the benefits of using water more efficiently. To check out more water-energy tools, click here.

Clicking through the links above or scrolling below will lead you to a descriptions of each tool, including links to download Microsoft Excel versions of each model. For each tool, users enter data on the left-hand side of the screen and the results display to the right. The data and assumptions behind each model can be viewed by clicking on the “Assumptions” tab in the bottom left corner of each workbook. Please note that these models are designed for educational purposes and are not intended to provide a comprehensive analysis of a given scenario.

A few of the questions these tools are designed to answer include:

Showerhead Comparison Calculator

The Showerhead Comparison Calculator is designed to compare the water, energy and carbon costs of showerheads with different water efficiency ratings. The calculator is targeted toward residential water users and provides a potent tool for educating the public on the energy and greenhouse gas emissions associated with their water use, since showering is among the most energy-intensive end uses of water.

Users begin by selecting the appropriate state to determine the carbon intensity of their electric grid. If using a natural gas water heater, click on the “Natural Gas” tab at the bottom of the page to open the natural gas worksheet. After selecting the flow rate of their current showerhead, users then fill in the number of people in their household, the number of showers each person takes per week, and the duration of each shower. The user then selects the flow rate of a more efficient showerhead to determine the water, energy and greenhouse gas emissions they could save. Users are encouraged to adjust the frequency and length of their showers to compare how showering habits can affect their water and energy use, in addition to using a more efficient showerhead.

Download the Showerhead Comparison Calculator

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Community Water-Energy Savings Calculator

The Community Water-Energy Savings Calculator provides an estimate of the amount of water, energy, CO2 and money saved by community-wide indoor water efficiency improvements. After selecting the appropriate state, users can select from five different residential indoor end-uses of water – toilets, showerheads, dishwashers, clothes washers and faucet aerators – to assess the relative savings of conservation programs aimed at improving the efficiency of each type of water use.

The amount of energy "embedded" in your water supplies is called the “energy intensity value” and it varies from city to city. For the purposes of this tool River Network has used values based on national averages, but if you want more accurate estimates you should contact your local water and wastewater utility to determine the actual energy intensity of their water systems. After filling in water system energy intensity values, the user then selects the size of their community or program target group and the anticipated market saturation of the product, or the percentage of households the target community that are expected to install the device. This allows users to compare the savings that would result from varying levels of program participation, as well as the relative savings achieved from different water efficient devices. Click on the “Assumptions” tab in the bottom left corner to view the data behind this model.

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Toilet Comparison Calculator

The Toilet Comparison Calculator is designed to compare the water, energy and carbon costs of toilets with different water efficiency ratings. Because toilets use only cold water, this tool is particularly useful for helping people understand the indirect – or upstream and downstream – energy and greenhouse gas emissions embedded in their water use.

After selecting the appropriate state, users then select the gallons per flush of their toilet based on the year the toilet was installed or manufactured. Users then provide information on the number of people in their household and the number of times each person flushes the toilet in a typical day. The final two inputs are the energy intensity of the local water supply system and wastewater treatment system, respectively. Although national averages are provided, users are encouraged to contact their local water and wastewater utilities to determine the energy intensity of their water systems, since these are the primary factors influencing the energy and greenhouse gas emissions embedded in the water used for toilet flushing.

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Water Heating Calculator

The Water Heating Calculator allows users to determine the energy and greenhouse gas emissions embedded in a gallon of hot water for a specific location in the United States. Because the temperature of water entering a home can vary significantly depending on local conditions, the amount of energy required to heat a unit of water can differ from city to city. All other factors being equal, the cooler the inlet water the more energy required to heat the water to a desired temperature. This calculator is designed for nonprofit organizations or utilities interested in determining the end-use energy savings that can be achieved in their community by reducing demand for hot water. This information is best applied in conjunction with data on the volume of water saved by end-use related to water conservation efforts.

Only two pieces of information are needed to run theWater Heating Calculator: the zip code and water heater temperature settings of the study area. For water heater temperatures settings, a default value of 140° F is provided although actual temperature settings may vary. A typical range for residential water heating settings is between 120° F and 140° F. After entering the zip code you wish to assess, users should enter a value that best reflects the average water heater setting of the community.

River Network would like to thank Pacific Institute for providing the data on inlet water temperature by zip code.

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New Water Source Impact Tool

The New Water Source Impact Tool is designed to provide a reasonable estimate of the energy and carbon emissions costs of developing a new water supply when detailed input data is unavailable. The tool relies on very basic assumptions and input data help communities assess the magnitude of energy required for water supply projects. This tool can be useful for water managers or nonprofit groups interested in estimating the costs of developing new water supplies and the cost-effectiveness of demand-side management to avoid the need to develop a new supply.

After selecting the appropriate state, the user then selects the type of water being developed (surface, groundwater, seawater, etc.) and the volume of water expected to be supplied through this source. Users are then asked to enter the elevation lift from source water to the distribution area. This information can typically be obtained through environmental impact statements or by contacting your utility. Next, users submit a value for the energy intensity of their distribution system, that is, the infrastructure that connects a major water supply to the houses and businesses that use the water. If your utility does not have this information, a proxy value is provided.

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