System size
Solar water heating systems are sized according to demand for hot water. The more hot water you use, the larger the storage cylinder and collector panel area should be. The number of people living in your house is a good guide for how large the system should be.
| Number of occupants | Cylinder size (litres) | Collector panel area (m2) |
| 3-4 people | 200-270 | 2.5 to 5 |
| 5-6 people | 270-360 | 3.75 to 6 |
These numbers are a rough guide only. The actual cylinder size and collector area you need will depend on your individual household situation, the system you choose, and the way it is configured. We recommend you discuss this with your supplier or installer to ensure you get a system that will meet your requirements.
'Open loop' and 'closed loop' systems
In some solar water heating systems, water is circulated through the collector panels and heated directly before being returned to the hot water cylinder. These are known as 'open loop' systems.
50.jpg "Open loop system with pump circulation")
Open loop system with pump circulation (image from EECA).
In other systems, a heat transfer fluid (usually a mixture of water and glycol) circulates through the collector panels. This fluid then passes through a heat exchanger in your hot water cylinder, heating up the water in your cylinder. There's no mixing between the heat transfer fluid and the water stored in your cylinder. This type of system is known as a 'closed loop' system.
Discuss with your supplier or installer whether either option is more suited to your requirements.
50.jpg "Closed loop system with pump circulation")
Closed loop system with pump circulation (image from EECA).
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