The rule establishes a statewide implementation schedule by which ultra-low NOx water heaters are required to be sold and installed throughout the state. As proposed, the rule will be implemented in Box Elder, Cache, Davis, Salt Lake, Tooele, Utah, and Weber counties beginning 01/01/2017; in Washington, Duchesne, and Uintah counties beginning 01/01/2018; and the rest of the state beginning 01/01/2019. Emission limits established in the rule are as follows: most residential water heaters are limited to 10 ng/Joule; larger commercial units are limited to 14 ng/Joule; and mobile homes and pools are limited to 40 ng/Joule. Ultra-low NOx water heaters are already readily available in California, and a limited number of residential units are available to Utah consumers through on-line purchases at prices comparable to similar units that do not meet the ultra-low NOx limits. The Division of Air Quality has requested additional cost information from residential and commercial builders, major box stores, and plumbing supply houses located in Utah, and has not received any additional information yet. Consequently, the agency is asking for additional cost and supply information during this public comment period.