The Tankless High Efficiency Condensing Ultra-Low NOx water heaters are available in three sizes of indoor and outdoor models, at 160,000, 180,000 and 199,000 Btu — the largest size can be used for both residential and commercial applications. The three units feature the latest in tankless technology, are highly efficient, and meet the low-NOx regulations and lead-free standards for California and Texas. All models are Energy Star® qualified and operate at a 0.95 energy factor (EF). The new models function with continuous maximum flow rates up to 10 gallons. They are manufactured with a durable double heat exchanger: a primary one made of HRS35 copper for resilience against erosion, as well as a secondary heat exchanger made of 316L stainless steel for protection against corrosion. Indoor models come equipped with a power cord and built-in temperature controller and diagnostic. Outdoor models come with a temperature remote controller. All residential units are covered under a 12-year limited warranty. There is a five-year warranty for products in commercial applications.