Can I use Solar Hot Water to heat my home?


No matter how optimistic you are, you will recognise that the Sun’s heat is least effective at the time you most want to heat the space you inhabit. The winter Sun is at its least warm and the days are short and the time of day you sit down and need it to be comfortably warm is at night when the Sun doesn’t shine. To accumulate the Sun’s heat in a solar hot water system in colder parts of Australia where we need winter heating you could reasonably expect to get the water to about 30-35 degrees, but if you run this through radiators designed to give off that heat a 400 litre water tank would not take many minutes to expend all its useful heat.

Solar and space heating

The most effective way to use the Sun to heat you home is by designing your home to have large double glazed windows on the Northern side of you home and appropriate eves to shade in the summer and a heat bank such as a concrete floor or a brick wall warmed by clerestory windows facing North. In Germany where people seem to be prepared to spend a lot of money on solar applications they use evacuated tubes to build heat in a heat bank such as a floor during the day and that warmth is available during the night, but there is a problem in the summer as to how to dissipate that heat.

If you are working with an existing home that cannot be modified to use passive solar heating then you best option is to draught proof, double glaze and insulate your home and find an appropriate form of space heating.

Many people with solar hot water systems use a slow combustion wood fire / stove to do the winter boosting of their domestic hot water as the time of year you need to boost your solar hot water coincides with the time of year you need to heat your home. A 4 or 5 kW wetback (water jacket) will be very effective in bringing the solar pre-heated hot water to the required temperature if that fire is lit every winter’s day / night. If you want to run hydronic heating from the slow combustion fire too then you simply increase the size of the fire and its boiler (wetback).

Woodfired hydronic heating

Having come to the conclusion that a wood fired hydronic heating system is something you wish to consider (hopefully on the basis that you have access to free wood, as bought firewood is expensive) then the sequence of your decision making is important. Our experience tells us that many people fall in love with the fire they wish to have in their home and then try to make it do things that it has not the capacity to. So the way to start this process is to work out where you want radiators (or zoned slab heating) then send us a plan of your home with dimensions clearly stated ( especially ceiling heights) and we will then do the calculations as to your heat requirements (kWs) and present you with a fully costed materials for a hydronic heating system including an appropriately sized wood fire boiler, radiators, piping, pumps, thermostat and a suitable solar hot water system which will receive winter boosting when the boiler is on.

Best Solar Hot Water will prepare a fully costed materials hydronic heating proposal for a fee of $50 including GST. Please complete the following questionnaire (add download link here) and send it to us by email together with a plan of your home and any additional information that you consider relevant.

If you wish to discuss your special circumstances then complete the Consultancy Request Form and once you have paid that fee ($50) we will call you for a 30 minute consultancy. The more information you give us on the Consultancy Request Form the more productive the 30 minute call will be.

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