Simplifying Natural Gas Water Heater Retrofits

Ben Schoenbauer — Jul 2014

Project Update

This project assessed the performance of hybrid water heaters to determine whether they are a good alternative to other high-efficiency models. Monitoring completed at four houses found that they eliminated almost all of the performance concerns and greatly reduced installation cost. Although overall payback of 10 years is still on the high end, hybrid water heaters provide a good option for many homes.

Project Summary

CEE’s recent field monitoring projects demonstrated the savings and performance of natural gas tankless and high efficiency storage water heaters. Despite substantial savings, system paybacks were long due to high installation costs in many retrofit applications. NorthernSTAR lab tests have demonstrated that improved insulation, smaller storage volumes, and controls are the most likely solutions to reduce energy losses and improve performance.

The majority of residential water heaters sales are retrofits or replacements, but most high-efficiency units require larger gas lines. One that could operate on a standard ½” gas line would reduce the difficulty and cost of installation and increase implementation. One manufacturer has two new units designed for easy retrofit installation by operating with ½” gas line, but has been unable to conduct fully monitored field tests under real occupant loads. This research project will determine how lower-input burners with smaller gas line sizing needs impact water heater economics in a retrofit

This study will install units in five single-family homes, then monitor them for the next six months to characterize their savings potential, installed efficiency, and ability to meet household demands. In addition, the project will determine whether these water heaters can meet typical residential hot water loads and solve comfort issues including slower ramp-up times and inconsistency. It will collect data including hot and cold water usage, inlet and outlet water temperature, and gas and electric usage. It will also investigate the impact smaller gas lines have on installed cost and the overall cost-effectiveness of these units, and how they impact hot water quality issues like cold water sandwich and low flow performance. An occupant survey will help determine user acceptance.

The final report will detail findings, including results from occupant surveys, and determine where these heaters are applicable and what portions of natural gas water heating sector still need a cost-effective solution.

This project is supported by Building America, as part of the NorthernStar project team.