Rheem RTGH-95XN Prestige Outdoor Tankless Water Heater, Natural Gas 8.4 GPM at a 45 degrees F temperature rise (up to 9.5 GPM at 35 degrees F) 94% Energy Factor (EF) with efficient stainless steel condensing heat exchanger Industry best 0.26 GPM minimum flow rate and 0.40 GPM minimum activation flow rate High-altitude capability, up to 9,480-ft elevation above sea level without a chip Low Nox burner meets SCAQMD rule 1146 requirements