Aquastar 125FX tankless water heater is compatible with solar and wood heating systems and can run on natural gas or propane. Weighing in at 51lbs, this water heater measures 29 3/4" x 18 1/4" x 8 3/4" has a water pressure range of 18 to 150 psi. Minimum flow rate is 0.5 gallons per minute and BTU input is 125,000. Featuring a water and gas inlet connection of 1/2" NPT, the minimum requirements for natural gas line is 3/4" NPT and minimum LP gas line is 5/8". Minimum LP gas pressure is 11" WC and minimum natural gas pressure is 7" WC. THE AQUASTAR 125FX OFFERS 80% ENERGY EFFECIENCY AND AN ENERGY FACTOR OF .78!