Navien NPE-24AWE Low-NOx Advanced LPG Gas Water Heater - Advanced Efficiency for Residential and Commercial Use The Navien NPE-24AWE Advanced LPG Gas Water Heater is a high-efficiency tankless water heating solution, the best selling tankless water heater in North America for over 10 years. Homeowners and businesses around the world trust this advanced system for on-demand hot water. Key Features and Benefits Energy-Efficient Design: Dual stainless steel heat exchangers for maximum performance and durability, minimum energy consumption. ComfortFlow® Technology: Integrated buffer tank and recirculation pump eliminates the cold water sandwich effect, hot water on demand and water saving.