AQUAH natural gas tankless water Heater, 3.2 gal (12 L)/min or 192 gal/hr, automatic electrical pulse ignition with no standing pilot, no electric Hookup necessary, operated by 2 D batteries or by 110 V AC as alternative, free AC Adapter, IC water control device, thermal efficiency >=85%, 24,000 Watt / 81,946 Btu/h thermal input, 45* temperature rise at 3.2 gpm flow rate, 25 to 110 water pressure for operation, 2000 Pa (0.29 psi) gas pressure, 1/2" water inlet/Outlet, 1/2" gas inlet, Winter/Summer control; Min/Max Water/Gas flow adjustment, dimensions: 24" H x 13 3/4" W x 7" D, net weight: 24 lb, requires 4" double wall type B vent pipes (not included).