Hot Water Basics

Solar hot water systems use the energy of the sun to heat water at a greatly reduced cost, compared to non-solar hot water systems. How do they work exactly? Solar hot water systems heat water by passing water through solar power collectors located on a roof. The main types of collectors used in solar hot water systems are flat plate and evacuated tube. To work effectively, solar hot water systems need unshaded North or West facing roof space.

Solar hot water systems are made up of three components: a storage tank, solar collectors, and a natural gas or electric booster. Water circulates between the storage tank and the solar collectors in the morning, until the radiant heat of the sun heats the water to around 50°c. This process continues until late afternoon. If the water in the storage tank is not at 50°c when hot water is required (eg. at night), the water is automatically bypassed through a gas or electric booster, which ‘boosts the water temperature to the required temperature. Watch our solar hot water video.

Many new homes these days come standard with solar hot water systems. However, these systems are generally low performing ‘builders-spec’ solar hot water systems that are ‘token’ in their solar performance. That is, they produce very little actual ‘solar’ hot water – most of the hot water is just heated by the gas or electric booster. Upgrading to a 2-collector solar hot water system can greatly improve performance and the energy saving you will make. Better still, choose an evacuated tube solar hot water system that performs well all-year round, even in overcast conditions, and that is less costly to repair in the event of breakages.

Other things to consider when buying a hot water solar system is the capacity of the booster (make sure you have a booster capable of producing at least 26 litres of hot water per minute) and the size of the storage tank (the larger the storage tank, the more free solar hot water you are able to store before relying on boosting). Also think about future owners of your home when sizing your hot water system.