The 24-panel, gravity fed solar-thermal system on the roof of the ARC preheats domestic cold water prior to its introduction into the steam-powered heat exchanger for domestic hot water, which significantly reduces steam usage for domestic hot water during normal operating periods. There are three main areas of hot water usage (domestic, pool, and air heating), but domestic (i.e. showers and sinks) represents the most pressing need and efficient use of solar technology.