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      WATER AND ENERGY SAVINGS FROM ON-DEMAND AND HOT WATER RECIRCULATING SYSTEMS

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          Abstract

          Electric hot water recirculation and on-demand instant hot water systems have been identified as “green” water systems due to purported energy and water savings, and some municipalities and districts even require green systems in residences. The performance of these devices have never been rigorously tested and evaluated. This work aims to address that gap by conducting a comparative, head-to-head study evaluating energy efficiency, temperature profiles and consumer issues such as cost and quality of system for two “green” water heating systems as compared to a standard water heater. Not only did the standard system outperform the hot water recirculation system with respect to temperature profile during flushing, but the standard system also operated with 32–36% more energy efficiency. Although the recirculation system did in fact save some water at the tap, when factoring in the energy efficiency reductions and associated water demand, recirculation systems actually consumed up to 7 gallons more water per day and cost consumers more money. On-demand systems operate with virtually 100% energy efficiency, but cannot be used in many circumstances dependent on scaling and incoming water temperature, and may require expensive upgrades to home electrical systems and use of low/ultra low flow showerheads. Although additional research is necessary to better understand nuances of electric water heating in the context of the water-energy nexus, this research provides a first step for rational decision making by regulators, public health officials, manufacturers and consumers.

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          Most cited references 3

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          A REVIEW OF THE SUSTAINABILITY OF RESIDENTIAL HOT WATER INFRASTRUCTURE: PUBLIC HEALTH, ENVIRONMENTAL IMPACTS, AND CONSUMER DRIVERS

           Randi H Brazeau (corresponding) ,  Marc Edwards (2011)
          Residential water heating is linked to the primary source of waterborne disease outbreaks in the United States, and accounts for greater energy demand than the combined water/wastewater utility sector. Furthermore, home water heating is the second largest energy consumer in the home and thus represents an integral part of the water-energy nexus. To date, there has been little practical research that can guide decision-making by consumers, public health officials and regulators with regards to water heater selection and operation to minimize energy costs and the likelihood of waterborne disease. Scientific uncertainties associated with existing “green” advice have potentially created misguided policy with long-term negative repercussions. This review is aimed at defining the current state of knowledge related to hot water infrastructure and in highlighting current gaps in the research. While there are many sustainability claims of certain water heater types (i.e., hot water recirculation systems and instantaneous water heaters) these claims have not been substantiated in head-to-head testing of the interplay between water temperature, energy, microbial growth, and scaling, all measures that need to be better defined.
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            Water and Energy Savings using Demand Hot Water Recirculating Systems in Residential Homes: A Case Study of Five Homes in Palo Alto, California

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              Sustainability of Residential Hot Water Infrastructure: Public Health, Environmental Impacts, and Consumer Drivers

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                Author and article information

                Journal
                jgrb
                Journal of Green Building
                College Publishing
                1552-6100
                1943-4618
                1943-4618
                Winter 2013
                : 8
                : 1
                : 75-89
                Author notes
                aCorresponding Author: Metropolitan State University of Denver, Denver, CO, USA 80217, rbrazeau@ 123456msudenver.edu , 00-1-303-556-2699 (p); 00-1-303-556-4436 (f).

                bVirginia Tech, 418 Durham Hall, Blacksburg, VA, USA 24060, edwardsm@ 123456vt.edu .

                Article
                jgb.8.1.75
                10.3992/jgb.8.1.75
                © 2013 College Publishing
                Page count
                Pages: 15
                Product
                Categories
                RESEARCH ARTICLES

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