At 0.99 Energy Factor, Navien’s NPE-S series condensing tankless water heaters are the most efficient models available.They supply maximum inputs from 150,000 to 199,900 Btu/hr., and efficient outputs from 148,500 to 197,900 Btu/hr. Maximum flow rates are from 8.4 to 11.1 gpm. Other features include 1/2” gas pipe capability up to 24’, 2” PVC venting up to 60’, dual stainless-steel heat exchangers, field gas convertibility and cascade up to 16 units without an external control box. NPE-S is ideal for most applications, especially commercial installations when a consistent and endless hot water outlet temperature is desired or required. When used in commercial applications such as a wash-down or cleaning operation as one example, the appropriate count of NPE-S tankless will assure adequate and continuous hot water at the temperature needed.