Compact solar water heater is a kind of solar water heating system that solar collector and storage are connected together with the cylinder storage on the top and collector panel on the bottom. There is no need of pump to push the fluid and no need of pipeline between the collector and storage. It is a simple and safe solution to get heat power from the sun.

The compact solar water heaters relies on the natural circulation of water between the collector and the tank or heat exchanger. Compact Solar Water Heater relies on warm water rising, a phenomenon known as natural convection, to circulate water through the collectors and to the tank. As water in the vacuum tubes is heated it rises naturally into the tank, while cooler water in the tank flows down to the bottom of the vacuum tubes, causing circulation throughout the system.

Compact Solar Water Heater move household water or a heat-transfer fluid through the system without pumps. This kind of passive systems have the advantage that electricity outage and electric pump breakdown are not issues. This makes passive systems generally more reliable, easier to maintain, and possibly longer lasting than active systems. Passive systems are often less expensive than active systems, but are also generally less efficient due to slower water flow rates through the system.