How Saving Water Improves Energy Efficiency

Michael Tobias
5 Minutes Read
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    Multifamily and office buildings account for 90% of water use among large buildings in New York City. In addition, buildings with automatic water meters that are subject to the Benchmarking Law (Local Law 84 of 2009) must report water consumption each year, and the results have revealed that multifamily buildings consume eight times more water than office buildings. Therefore, water conservation efforts can have the greatest effect if focused on the multifamily housing sector.

    • According to building benchmarking data, the average Water Use Intensity (WUI) for multifamily buildings in NYC is 50 gal/ft2. However, some properties exceed 300 gal/ft2.
    • Office buildings, which follow multifamily  buildings in terms of consumption, typically have a WUI below 20 gal/ft2, and the properties with the highest WUI reach up to 140 gal/ft2.

    Although environmental sustainability is the main driver for water conservation in NYC, energy savings are also achieved in the process. Water conservation reduced pumping expenses, and domestic hot water systems also experience a reduced heating load. Consider that domestic hot water represents the fifth-largest energy use in NYC, accounting for 11% of energy use in large buildings overall and up to 19% in multifamily buildings. The emissions reduction potential is also significant, since most water heating in NYC is accomplished with either natural gas or fuel oil.

    Water conservation measures can achieve synergy with point-of-use water heaters, which eliminate the standby losses of storage heaters, as well as piping losses when hot water must travel a long distance between a heater and a fixture.

    Importance of Reliable Water Consumption Data

    Measurement is the first step to achieve control over any variable, and water consumption in a city is no exception. To improve its billing capabilities, the NYC Department of Environmental Protection is installing automatic meter reading (AMR) devices. These units are equipped with a low-power radio device and communicate with a network of receivers installed throughout the city, with collaboration from the Department of Information Technology and Telecommunications. The DEP can become much more efficient with AMR units, since its staff must no longer visit properties to take manual readings.

    Another advantage of AMR devices is that they integrate with a web application that can be accessed by property owners to better manage their water consumption. They can view how water consumption is distributed by day, week, month and year. In addition, the Benchmarking Law covers water use in individual buildings above 50,000 ft2, as well as groups of buildings above 100,000 ft2 under the same tax lot or condominium ownership - valuable water consumption data is being gathered. AMR devices will be installed for more than 830,000 properties in NYC at zero cost for their owners.

    Improving Plumbing Fixtures in Multifamily Buildings

    The US Environmental Protection Agency launched its WaterSense program for plumbing fixtures, which labels products that offer demonstrated water savings compared with conventional fixtures. Properties classified as affordable housing are also eligible for Con Edison rebates covering 100% of the cost of some plumbing fixture upgrades.


    According to the US EPA, showering accounts for around 17% of water use in residential settings, representing around 40 gallons per day for the average US family and 1.2 trillion gallons per year for the entire country. As a result, improvements to showerheads have a significant potential to save water.

    A conventional showerhead built according to 1992 standards uses water at a rate of 2.5 gallons per minute (gpm), and this value can be even higher for older units. However, shower heads with a WaterSense label use below 2.0 gpm, and also have a uniform spray pattern - surveys carried out by the US EPA indicate that homeowners prefer a uniform pattern over a concentrated jet of water or a ring-shaped spray. WaterSense showerheads have also been tested by approved third-party agencies to validate their performance.

    By upgrading to WaterSense showerheads, the average US family can save 2,900 gallons of water per year, and more than 370 kWh of electricity on water heating. Throughout the country, this benefit could add up to $2.2 billion in water bills and $2.6 billion in energy bills.

    Multifamily buildings in New York City that are classified as affordable housing are eligible for free showerhead upgrades for dwelling units. The Con Edison incentive program provides a rebate covering the full upgrade cost of up to two showerheads per dwelling as long as their water use is below 1.5 gpm, surpassing the requirements of the US EPA WaterSense program


    Toilets are the plumbing fixtures that consume the most water in residential settings, accounting for 30% of use. The federal standard is 1.6 gallons per flush, but the WaterSense labels requires 1.28 gallons per flush or less. Savings are even higher when replacing old toilets, which can consume up to 6 gallons per flush. In other words, a WaterSense toilet provides 20% water savings when replacing a unit meeting federal standard, and up to 80% when replacing old and inefficient units.


    WaterSense faucets only use 1.5 gpm, achieving significant savings compared with faucets built according to the federal standard of 2.2 gpm. If every faucet in the country was upgraded to a WaterSense unit, it would be possible to save more than $1.2 billion each year in water and energy bills.

    Like in the case of showerheads, NYC multifamily buildings classified as affordable housing are eligible for free upgrades through the Con Edison incentive program. Each dwelling unit can receive up to four faucet aerators installed for free, as long as the following water use requirements are met:

    • 1.5 gpm for kitchen faucets
    • 1.0 gpm for bathroom faucets


    Water conservation measures achieve direct savings by reducing water bills from the Department of Environmental Protection, and indirect savings from a reduced water heating load. Property owners planning to upgrade their domestic hot water systems could optimize their investment by first focusing on water conservation, which may allow them to purchase new water heaters that are both smaller and more efficient. The services of a professional consultant or engineering firm are highly recommended to find the combination of upgrades that yields the highest return on investment.

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    Tags : Design Sustainability Construction

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