[File:Active Indirect Water Heater Diagram.svg|right|400px|thumb|1: Municipal water feed 2: Fluid from water storage tank to external (passive) heat source; passive heat source can be the ground (soil or groundwater), sun or air via heat pump, or thermodynamic solar panel 3: Fluid from heat pump, or thermodynamic solar panel to water storage tank 4: Pump, actuator, controller and other parts 5: Water heater 6: Water storage tank 7: Hot water to domestic appliances]]