The Hayward H-Series heater is designed for “universal” energy efficient used for any types of pool. The hydraulic design of the Hayward Universal heater provides energy efficiency of up to 18%. Its an environmentally friendly low NOx emission, a perfect choice for the environmental friendly pool owner. The design on the Hayward Universal H-Series heater has flexible connection options make them ideal for any types of pool equipments. Options include 250,000 and 400,000 BTU natural gas or propane models.