WATER HEATING

This 2004 guide by RMI provides homeowners with strategies to reduce water heating costs and energy consumption through the use of efficient fixtures, maintenance of existing heaters, and the adoption of advanced heating technologies such as solar thermal, heat pumps, and drain-water heat recovery.

• Water heating is typically the second largest energy user in the home, representing about 19 percent of total home energy use and costing an average household more than $300 annually. In the United States, approximately 38 percent of homes use electric water heaters, which can cost more than twice as much to operate as natural gas heaters.
• Installing water-efficient fixtures and appliances can significantly reduce consumption. The EPA estimates a four-person household can cut water use by one-third with efficient fixtures and appliances. Replacing fixtures older than ten years with modern low-flow versions can achieve water savings of 25–60 percent, with some faucet flow controls reducing flow to between 0.5 and 1 gpm.
• Homeowners can reduce energy bills through simple adjustments to existing heaters: lowering the temperature to 115–120°F can save up to 5 percent for every 10-degree reduction; adding an insulating jacket (at least R-8) can reduce heat loss through tank walls by 25–45 percent and save 4–9 percent of costs; and installing timer controls for electric heaters can save an additional 5–12 percent.
• Demand or tankless water heaters are more efficient than storage tanks. For high-water-use homes (approx. 86 gallons/day), they are 8–14 percent more efficient; for low-water-use homes (41 gallons/day or less), they are 24–34 percent more efficient. Using on-demand heaters at each individual water outlet can increase savings to 27–50 percent.
• Heat pump water heaters are 33–50 percent more efficient than electric water heaters because they move heat from the air or ground rather than heating water directly. In hot climates, integrating space cooling and water heating with a heat pump can save 25–70 percent of the energy used by a typical electric water heater.
• Drain-water heat recovery systems, specifically gravity film exchange systems, can save 25–30 percent of total water-heating energy by capturing heat from water going down the drain. These systems typically cost between $300 and $400 with payback periods ranging from 2.5 to 7 years.
• When replacing an electric water heater, switching to a standard gas tank is highly cost-effective, offering annual savings of $142 with a payback period of 0.4 years. In contrast, replacing a standard gas heater with a high-efficiency gas heater saves only $25 annually and has a payback period of about 12 years.

APA

Goorskey, S., Smith, A., & Wang, K. (2004). WATER HEATING. RMI. https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_HEB5WaterHeat.pdf

Chicago

Goorskey, Sarah, Andy Smith, and Katherine Wang. WATER HEATING. RMI, 2004. https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_HEB5WaterHeat.pdf.

Wikipedia

{{cite report |last1=Goorskey |first1=Sarah |last2=Smith |first2=Andy |last3=Wang |first3=Katherine |title=WATER HEATING |publisher=RMI |date=2004 |url=https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_HEB5WaterHeat.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{goorskey2004water, author = {Goorskey, Sarah and Smith, Andy and Wang, Katherine}, title = {{WATER HEATING}}, institution = {RMI}, year = {2004}, url = {https://rmi.org/app/uploads/2017/05/RMI_Document_Repository_Public-Reprts_HEB5WaterHeat.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }