INSTANT HOT WATER FOR LARGER HOMES:This indoor natural gas tankless water heater delivers instant hot water on demand with a powerful 4.3 GPM flow rate and 102,000 BTU heating capacity, providing endless hot water for 3–4 fixtures simultaneously. Ideal for showers, kitchens, and bathrooms in larger residential homes. INTELLIGENT CONSTANT TEMPERATURE CONTROL:Equipped with advanced intelligent temperature regulation and Constant Temperature PLUS technology, this natural gas tankless water heater automatically adjusts the air-fuel ratio to maintain stable water temperature within ±1℉, even when multiple outlets are used at the same time, helping prevent sudden temperature fluctuations and scalding. HIGH-EFFICIENCY PURE COPPER HEAT EXCHANGER:Constructed with a 100% pure copper heat exchanger, this indoor natural gas water heater delivers up to 95% thermal efficiency, reduces heat loss, provides hot water within seconds, and ensures reliable performance with long service life. MULTIPLE SAFETY & ANTI-FREEZE PROTECTIONS FOR INDOOR USE:Designed for indoor installation, this tankless gas water heater features overheat protection, flame failure protection, anti-dry combustion, dual gas solenoid valves, leak detection, and automatic freeze protection with built-in heating modules that activate below 39°F (4°C) for safe winter operation. COMPACT WALL-MOUNTED DESIGN & EASY INSTALLATION:Featuring a compact, space-saving wall-mounted design (21.3″H × 13.7″W × 6.8″D), this indoor tankless water heater supports standard 3/4″ NPT water and gas connections, 3″ vent, and a UL-approved 120V power supply, making it suitable for apartments, condos, and residential homes without major modifications. Designed for higher demand, this natural gas tankless water heater delivers a strong 4.3 GPM flow rate with 102,000 BTU, making it suitable for 3–4 fixtures at once. Enjoy continuous hot water without storage limitations. The pure copper water tank ensures durability and fast heating, while constant temperature technology provides a safe and comfortable hot water experience. Equipped with a 3/4" NPT connection, it integrates easily into standard indoor plumbing systems. Its energy-saving, compact design makes it a smart choice for larger apartments or homes that require higher hot water output using natural gas.