The Smart 316 Stainless Steel Indirect Fired Water Heater is heated by the hot water from your boiler. As your home is being heated, your domestic hot water is being heated at the same time, thereby, consuming less fuel and conserving energy. Combine this with a recovery rate that is up to three times faster than conventional gas or electric water heaters, and The SMART 316 Series Indirect Fired Water Heater heats more hot water with less fuel for the energy conscious consumer. The average life span of a SMART 316 Series Indirect Fired Water Heater exceeds 20 years! That is two or three times the average life of a conventional gas, oil or electric water heater.