Active solar water heating systems use mechanical pumps and differential controllers to manage the flow of heat-transfer fluid or water from the solar collector to the storage tank. These controllers monitor temperature differences between the collector and the tank. When the temperature of the water in the collector is higher than that in the tank, the system activates the pump to transfer heat efficiently. The pumps in active systems can be powered either by mains electricity or by solar photovoltaic (PV) panels. Some systems rely entirely on solar energy to circulate the fluid during daylight hours, storing the heated water in well-insulated tanks for use during the night. Others include a mains-powered backup to ensure consistent operation during cloudy days or at night. Unlike passive systems, active systems do not rely on gravity for fluid movement, which allows greater flexibility in tank placement. Storage tanks can be located inside attics or other insulated indoor areas to reduce heat loss. These tanks can also be integrated with existing hot water cylinders, allowing the solar system to preheat water for household space heating—especially beneficial during winter months. Active solar systems offer greater efficiency and flexibility, making them ideal for homes requiring reliable year-round hot water.