How Much Does a Tankless Water Heater Save?

Tankless water heaters provided measured savings of 50 to 85 therms per year, a significant amount of energy. They produce hot water differently than storage water heaters, creating some changes in user behavior. These changes do not force users to increase hot water consumption. Homeowners considered TWHs’ ability to provide endless hot water and their consistent and steady temperatures as performance benefits. Users disliked their delayed delivery time and need to increase flow for low flow operations. Most homeowners found the positives outweighed the negatives, and nine of the ten homes opted to keep the TWH. The economics of TWHs are poor for retrofit applications where a conventional storage heater can operate safely. In these scenarios, TWHs will not pay for themselves in their lifetimes without significant reductions in installed costs or a major increase in natural gas prices. Homes with higher usage rates have improved paybacks. The economics of TWHs are more favorable for new construction and for retrofit applications where power vented water heaters are required to ensure adequate venting. In these applications, incremental costs for TWHs can sometimes be reduced to $0 and paybacks range from 0 to 18 years. This research demonstrates the inability of the Energy Factor test to compare water heater performance for different technologies. The Energy Factor underpredicted savings for TWHs, projecting a 25% savings where a 37% savings was measured. References [DOE] U.S. Department of Energy. 2008. “ENERGY STAR® Residential Water Heaters: Final Criteria Analysis,” Washington, D.C.: U.S. Department of Energy. [EIA] US Energy Information Administration . 2009. “Residential Energy Consumption Survey, 2009” http://205.254.135.7/consumption/residential/ Washington, D.C.: U.S. DOE.