Similar to space heating, water is heated in the building for various uses including cooking, cleaning and bathing. A water heater is an appliance that typically uses either a gas burner or an electric heating element to heat water. 

According to U.S. Department of Energy (DOE) and various surveys like Residential Energy Conservation Survey, water heating solely uses more than 20% of a home's energy use. For a K-12 school, as per the Advanced Energy Retrofit Guide, while the percentage might be lower as compared to homes, water heating along with some other plug loads can account for up to 15% of the building energy use. Additionally, the second largest end use of natural gas in various buildings is water heating. 

There are three major ways of reducing water heating energy consumption: 

  1. Selecting the appropriate fuel and water heater type,
  2. Using an efficient system design, and
  3. Reducing hot water consumption.

Opting for a higher efficiency water heating system (for example, ENERGY STAR certified), improving the efficiency by insulating the existing storage tank (for example, adding an insulation blanket) and pipes (for example, insulating pipes in unconditioned space) and decreasing service hot water temperature or even installing automatic temperature controls wherever viable are various ways of minimizing the utility bills. 

Recommendations Provided (link each of them to the specific section in the article): 

  1. Install low flow water fixtures 

  2. Replace Service Hot Water Heater with High-Performance Condensing Hot Water System

  3. Replace Service Hot Water Heater with High-Performance Heat Pump Water Heater

Asset Score Report Recommendation:
Install low flow water fixtures 
Cost $

A low-flow fixture is a water-saving plumbing device that uses less water or a smaller amount per flush. Examples include showerheads, urinals, toilets and aerated faucets. 

Before 1980, toilets used either 7 gallons per flush (gpf) or 5gpf. The standard changed to 3.5gpf after 1980, and in 2002, the federal standard for new construction became 1.6gpf toilets, designed to increase flush velocity using gravity or pressurized flush water. DOE adopted a 2.2gpm (gallons per minute) for private-use lavatory faucets and kitchen faucets in 1998. Various aerators for faucets including a standard, spray, rain spray and laminar flow are available in the market with varying flow rates.

Upgrading older fixtures to meet this standard can lighten the utility load and lower facility costs. Various national level as well as U.S. Environmental Protection Agency's (EPA's) flow rates and specifications for faucets, showerheads and other fixtures can be found on the EPA website - https://www.epa.gov/system/files/documents/2023-06/ws-commercial-watersense-at-work_Section_3.3_Faucets.pdf. 

Water-saving fixtures not only decrease water usage but also reduce the energy required to heat the water. 

Resources: 

  1. https://www.homeinnovation.com/-/media/Files/Reports/waterheatingFS.pdf
  2. https://www.energy.gov/energysaver/reduce-hot-water-use-energy-savings
  3. https://www.energy.gov/energysaver/selecting-new-water-heater
  4. https://www.energy.gov/energysaver/articles/new-infographic-and-projects-keep-your-energy-bills-out-hot-water
  5. https://www.energy.gov/energysaver/articles/new-infographic-and-projects-keep-your-energy-bills-out-hot-water




Asset Score Report Recommendation:
Replace Service Hot Water Heater with High-Performance Condensing Hot Water System
Cost: $$

High-performance condensing hot water systems are designed to maximize energy efficiency and minimize heat loss. Unlike standard gas water heaters, condensing systems utilize a secondary heat exchanger to extract additional heat from exhaust gases. This translates to lower energy consumption and operating costs while still delivering the hot water needed for multifamily buildings.

These systems are particularly well-suited for applications with high hot water demand. such as multi-family buildings. By reducing wasted heat, they contribute to overall carbon emissions reduction. Additionally, condensing water heaters are compatible with existing natural gas infrastructure, making them a feasible upgrade for buildings transitioning toward more efficient systems. It is important to ensure proper venting and installation requirements, as these systems require venting with non-corrosive materials (e.g., PVC) to handle the low-temperature exhaust (https://www.energy.gov/femp/purchasing-energy-efficient-commercial-gas-water-heaters). With proper setup, they offer a reliable, high-efficiency solution for long-term energy savings and environmental benefits.

Resources: 

  1. https://www.energystar.gov/products/high_efficiency_gas_storage_water_heaters/how-it-works
  2. https://basc.pnnl.gov/building-science-measures/gas-storage-water-heater

 


Asset Score Report Recommendation:
Replace Service Hot Water Heater with High-Performance Heat Pump Water Heater
Cost $$

High-performance heat pump water heaters (HPWHs) use advanced technology to heat water efficiently by transferring heat from the surrounding air instead of generating heat directly. This results in energy savings of up to 70% compared to conventional electric resistance water heaters (https://www.energystar.gov/products/energy_star_home_upgrade/super_efficient_water_heater). By leveraging ambient air, HPWHs achieve impressive efficiency ratings and help utility costs.

In addition to energy efficiency, heat pump water heaters offer operational flexibility, as they often come with multiple modes (e.g., high-demand or energy-saver mode) to meet varying water usage patterns. These systems work best in spaces with moderate ambient temperatures and sufficient ventilation. For multifamily properties, HPWHs are a great option for aligning with sustainability initiatives.

HPWHs may require more space and slightly longer recovery times compared to traditional systems. However, with proper sizing and placement, they provide a long-term, eco-friendly solution for water heating. Furthermore, many units qualify for rebates or incentives, making the upfront investment more accessible for building owners.

Resources: 

  1. https://www.energystar.gov/products/heat_pump_water_heaters/benefits-savings
  2. https://basc.pnnl.gov/resource-guides/distributed-heat-pump-water-heaters-multifamily-buildings#edit-group-more-info
  3. https://www.energy.gov/energysaver/heat-pump-water-heaters
  4. https://www.energystar.gov/partner-resources/residential_new/educational_resources/sup_program_guidance/heat_pump_water_heater_guide