Solar thermal or solar hot water systems use the sun's energy to create hot water. For most people, the largest component of their utility bill is the cost of their hot water heater. A solar collector, as pictured below, is similar in appearance to a PV module. Fluid is cycled between a storage tank and the collector throughout the day as the sun's energy heats the collector. The heat is transferred to the water in the storage tank by the heated fluid cycling through either a coil inside the tank or an external heat exchanger. The storage tank is installed next to your existing water heater. Whenever more hot water is demanded, your hot water heater draws from this storage tank. The solar heated water will require little or no additional heating from your existing hot water heater, offering substantial savings on your utility bill.
These systems are typically less expensive and offer shorter payback times than solar electric systems. They are also able to capture solar energy with overcast or partially shaded conditions, unlike most PV systems.
Solar thermal systems can also be used for space heating in homes with infloor/radiant heat.
Most installed solar thermal systems are either pressurized glycol or closed-loop drainback systems. To learn more about solar thermal systems visit: Home Power Solar Hot Water Basics