The Smart is heated by the hot water from your boiler. As your home is being heated, your domestic hot water is being heated, 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 Series Indirect Water Heater heats more hot water with less fuel for the energy conscious consumer. The average life span of a SMART Series Indirect Water Heater exceeds 20 years! That is two or three times the average life of a conventional gas, oil or electric water heater.