1. A really good idea for controlling the solar hot water electric/gas boost is to simply use a timed switch. By default it is off, thus the hot water is not boosted when it gets below a certain temperature. However when required, the homeowner simply pushes in the timed switch and the water is heated for a short period of time, after that the switch automatically turns off and its solar only heating again. The switch is best installed where it is easily accessible (say the kitchen).
    A friend of mine (an electrician) uses this set up and it works brilliantly. It is a simple and cheap way around the problem of inappropriate boosting.
    The other thing that can be done to extend the solar hot water heating benefit is to have the temperature of the water in the tank at a higher temperature. Thus the water lasts long during overcast periods. Done correctly with normal household water usage and an appropriately sized tank, the hot water should last for a few days with no solar contribution during that period.
    Again, this is a simple adjustment which does not require any fancy electronics.

    • @Jason: Very good advice. Our system was off-peak. A timed switch would have been good, but if you forget one night then you have cold water and an angry wife until the next off-peak electricity period :-).

      If you have good solar exposure, a properly sized system, and generally decent weather (like here in the Illawarra), then it may actually make more sense to switch away from off-peak and use normal electricity for manual boosting only when required. Some people I know have this kind of setup, and really don’t need to boost very often.

  2. Good point about using normal tariff electric power. That is what he does. With off-peak power and manual boosting, then you are likely to run out of hot water.
    I use normal tariff electric hot water at the moment, and it is still fairly cheap. So it is certainly an affordable option for manually boosting solar hot water systems.

  3. Green Builder

    Hey thanks for the useful links you provided! I’m gonna be needing this handbook for my sister’s school stuffs. Great post by the way 🙂

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