Pentair PowerMax high performance swimming pool heaters run reliably on natural gas with efficiency of up to 85%. Finned, 10-tube heat exchanger provides the quickest and most efficient heat transfer in meeting the ASHRAE 90.1 standard for efficiency for use with storage tanks. The PowerMax pool heater can significantly cut fuel costs compared to conventional water heating systems. This pool heater is ready out of the box with factory preset automatic by-pass and combustion system. No field adjustments are required.