A. O. Smith's Signature Series Non-Condensing Ultra-Low NOx Indoor Tankless Gas Water Heater uses up to 190,000 BTU/h of natural gas or propane to deliver a 8 gallons per minute flow rate (based on a 35°F rise) of continuous hot water for your home when sized appropriately. This makes it a good match for whole home applications. A. O. Smith Tankless Gas water heaters only heat water when needed, making them one of the most energy efficient ways to heat water. This high efficiency non-condensing indoor model has a 0.82 Uniform Energy Factor (UEF) and can reduce your energy consumption and save money on your energy bills. Additionally, our Tankless Gas design can be easily wall-mounted indoors, saving you valuable storage space. This model may qualify for additional energy efficiency rebates and tax credits in your local area. See Lowe's Rebate Center for details. Not sure if this is the right water heater for you? Use our product selector tool to see if this model is the right fit for your hot water needs. Tankless gas water heaters have special installation requirements. Professional installation is required.