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8 REDUCE HOT WATER ENERGY BY 50%

This action focuses on reducing household energy by cutting hot water energy use in half.

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WHY?

Energy used for water heating accounts for 13% of all home energy use in the United States. To get an idea of how much energy water heating accounts for in your own home you can check your natural gas bill (if gas heated). A typical natural gas bill includes both space heating and water heating. In Minnesota, the heat may be on from November to April. By averaging out the months when the heat is off, you can get a typical value of water heating energy.

There are a few things anyone can do to reduce their water heating energy each month:

(1) Set your water heater thermostat to a lower setting. Typically, water heaters have three heat settings: high, medium and low which correspond to around 160° , 140° and 120°. With each 10 degree reduction, 3-5% of energy can be saved.

(2) Consider a timer for the water heater to turn off when not in use. While it may seem as through this would be a less efficient use of energy to re-heat water, Lawrence Berkeley Lab’s Home Energy Saver (LBL, HES) says it is not:

"...water heater energy consumption increases with higher water temperatures, and water heaters use more energy to heat water up and keep it hot than they do to heat it up once, because heat is lost through the walls of the tank in proportion to the tank temperature. The same energy is required to heat up the water regardless of whether it is heating a little bit at a time, or all at once. Heat losses through the tank walls or pipes simply add to the cost. So, turning the water heater off for a few hours each day actually saves some energy. This strategy works best for electric water heaters, because they lose heat less rapidly than gas or oil water heaters (LBL, HES).

If the water heater is off during the day, it would be an inconvenience if the occupant uses more hot water than is stored in the tank. Installing a timer that turns the water heater off or that lowers the temperature during the night generally poses no inconvenience at all. These timers can be set to turn the heater back on an hour or so before you get up in the morning."

(3) If your water heater is inefficient, or larger than your uses, consider one of these more efficient heaters, compiled by the American Council on an Energy Efficient Economy (ACEEE).

Beyond these steps, however, water heating energy can be reduced by a much more significant amount by changing your lifestyle habits. This action focuses on how to analyze water use and reduce 'hot water gallons' per day.


how to do this action:

The first step when choosing this action is to understand how much hot water is used for daily activities and to create a plan for cutting hot water energy in half. Over the course of a week, track your hot water use (in gallons) for each day. Time how long you typically take a shower, wash your hands (if using hot water), wash your face, run the sink for rinsing dishes, etc and fill out the spreadsheet at the end of this page. The following chart is an example of hot water tracking plan. Use chart 1 to track how long or how many times you use hot water for each task each day of the week. Use these averages to fill our Chart 2 and find how many gallons of hot water you use as well as the energy that is needed to heat this water.

Hot Water Tracking Plan

It is important to track not only how long hot water was running for each use but also the flow rate of each fixture. You can do this by holding a one-gallon bucket under the faucet and seeing how many buckets are filled while timing for one minute. A graphic interpretation of this chart is seen below:

Hot Water Tracking Plan

As you can see, in this example, showering or bathing use the most water each day. Another big user is clothes washing which typically uses warm or hot water. Other small uses include washing dishes, hand washing and face washing. In the plan shown (in blue), hot water gallons are reduced from an original or 32-42 gallons per day to the goal of 10 through the following changes:

  • - Clothes washing will be done on cold settings
  • - Bathing will be limited to 5 gallons of hot water per day. This means either taking a bath every other day or only running hot water for 2.5 minutes per shower (turning water faucet off and on during shower)
  • - All other uses are allowed to stay the same for the sake of simplicity.

This example may be fairly reflective of typical water use, but will likely vary from participant to participant. After analyzing your own hot water use, come up with a set of goals to reduce hot water energy by 50% each day.


what will be measured?

KEY QUESTIONS

QUANTITATIVE QUESTION: How much energy is saved by cutting hot water energy in half?

QUALITATIVE QUESTION: How does the experience of reducing hot water energy by 50% affect your happiness, convenience, health and costs?

BASELINE WEEK TRACKING

QUANTITATIVE
During the baseline tracking week before the project begins, use the corresponding spreadsheet (E8_BASELINE) to record how much hot water is currently used for each daily task.

The goal is to determine how much energy is currently being used to heat water on a daily basis. To raise one gallon of water 1 degree F requires 8.34 BTUs of energy. Assuming a typical incoming municipal water temperature of 55 degrees F and a final hot water temperature of 105 degree F (the temperature of a hot shower), 458.7 BTUs (0.1344 kWh) is required to raise each gallon of water to the desired final hot water temperature.

QUALITATIVE


Qualitative Scale

Using the above scale as a visual, rate each of the following criteria using the spreadsheet (E8_BASELINE) as it relates to your current hot water use:

  • 1. SATISFACTION/HAPPINESS
    (Overall, how much enjoyment or dissatisfaction do you get out of doing and completing this behavior?)

  • 2. CONVENIENCE
    (How easy/difficult and accessible/inaccessible is this behavior for you to do and complete?)

  • 3. HEALTH
    (How healthy/unhealthy and safe/unsafe does this behavior make you feel?)

  • 4. COST
    (How much does this behavior cost? Use positive numbers for being above average and negative numbers for being below average and zero for being average.)

IMPLEMENTATION PHASE TRACKING

QUANTITATIVE
Use the corresponding spreadsheet (E8_QUANTITATIVE) to create a plan for reducing hot water energy by 50%:

  • (1) Examine your baseline condition for the biggest users of hot water and re-report this information for comparison.
  • (2) Determine strategies to reduce or eliminate certain water tasks in order to reduce overall hot water use by 50%. List new lengths of time or times per day and a strategy for reduction.

  • ***NOTE: Keep in mind that not all tasks require hot water. If you are able to use unheated water instead, change length of time in the new use secion to a ‘0’ and be sure to list this as a strategy.***

  • (3)Use the spreadsheet to calculate your new plan for total hot water use, making sure it is a 50% reduction from your baseline.

QUALITATIVE
Part 1 - Ranking


Qualitative Scale

Using the above scale as a visual, rate each of the following criteria each week of the project on the spreadsheet (E8_QUALITATIVE) Your answers should not be rated in comparison to your baseline week, but in general as a reflection of how you are feeling.

  • 1. SATISFACTION/HAPPINESS
    (Overall, how much enjoyment or dissatisfaction do you get out of doing and completing this behavior?)

  • 2. CONVENIENCE
    (How easy/difficult and accessible/inaccessible is this behavior for you to do and complete?)

  • 3. HEALTH
    (How healthy/unhealthy and safe/unsafe does this behavior make you feel?)

  • 4. COST
    (How much does this behavior cost? Use positive numbers for being above average and negative numbers for being below average and zero for being average.)

Part 2 - Blogging
Keep a narrative log of your experiences changing this action in your life. Which uses of hot water did you find to be the biggest? Which uses were you able to reduce or eliminate? Which strategies invovled the most lifestyle change? Which involved the least? Did you find yourself making one large change or many small changes?


resources

Lawrence Berkeley Lab, Home Energy Saver
ACTION SPREADSHEETS

The spreadsheets referred to above can be found in the Excel file at the following link:

E8_Reduce Hot Water Energy By 50% Spreadsheet

If you prefer to enter your responses by hand, printable PDFs of each spreadsheet can be found at the following links (at the end of the project, all data will have to be entered into the Excel spreadsheet):

E8_BASELINE
E8_QUANTITATIVE
E8_QUALITATIVE