Navien NPE-2 series high-efficiency condensing tankless water heaters come in Standard (NPE-S2) and Advanced (NPE-A2) models up to 199,900 Btu/h that are highly efficient up to 0.96 UEF and field gas convertible from natural gas to liquid propane or natural gas high elevation operation. NPE-A2 models include patented ComfortFlow built-in recirculation pump and buffer tank that resolves issues of minimal flow rates commonly found in other tankless water heaters. NPE-2 features expanded cascade capability up to 32 units and common venting capability up to 12 units, and EZNav advanced multi-line control with built-in intuitive software and easy-to-use Setup Wizard.