A.O. Smith. The company’s new 180,000-BTU condensing tankless water heaters offer continuous flow rates of up to 8 gallons per minute and use highly efficient condensing technology, which allows the units to operate with an Energy Factor of 0.91. The manufacturer says an easy-to-read built-in display shows temperature, diagnostics, and error messages. The Energy Star–rated units are available in natural gas or propane as well as indoor and outdoor configurations. 800.527.1953.