Solar geyser

Solar geyser provides hot water for the home on every sunny day.

Solar tubes geyser.Solar geyser

Watch out for a tube that has lost its vacuum when installing a cheaper brand of dubious origin. The German make is 40% more efficient and has thicker glass in case of hail. We have both, so I can speak with some knowledge.

This page was last updated by Bernard Preston on 13th March, 2019.

By Bernard Preston

  1. Bernard Preston
  2. Our green home
  3. Solar geyser

It has been estimated that roughly half the electricity consumed in the modern home is used to heat water; in the geyser, washing machine and dishwasher. The single most cost-effective measure you can take to reduce your power bill is to install an efficient solar geyser.

I say efficient as many of them are something less than satisfactory; I recently met a couple who still have to use mains for four hours a day to heat the water for two people. In contrast, if we turn on the geyser for more than sixty minutes a month, and never in winter when it is cloudless, it’s a lot.

If we have guests to stay then it may be different.

The modern solar geyser uses vacuated tubes with a copper rod down the centre. Heat is trapped within the glass and conducted up the rod to a manifold containing water; it is extremely effective.

One of the great advantages over the old systems is that it is frost proof down to minus 10 degrees and less.

The hot water in the manifold then by convection rises to the geyser which needs to be placed at least some 60cm above the manifold.

In theory the geyser can be in the ceiling below the manifold, but I don’t recommend this. A solar pump must be used; they are noisy, expensive and don’t last very long; if the plastic fitting bursts, as ours did, your ceiling will be flooded. New building requirements in any event are for geysers to go on the roof; it’s rather unsightly, but it is effective and far more functional. No more flooding of your carpets and ceiling boards.

My recommendation is a 20-tube system; it’s only slightly more expensive, and you’ll have hot water throughout the winter when the sun is lower in the sky.

With a 150-litre geyser, enough for two days, we only rarely turn the geyser on, and not usually for more than ten to fifteen minutes; the water actually boils on occasion in summer.

A special geyser is required, with an extra inlet and outlet to the manifold.

Replacing a perfectly good geyser is probably a needless expense; rather start planning now, so that when your existing unit bursts, you are ready to move. They rarely last much more than five years.

My advice is to use the German solar tubes and manifold, supplied by a Pietermaritzburg company that has been in existence for many years; down the grapevine I hear the Australian and Chinese are less effective, but do your own homework.

Fitted, you are looking at about R30,000. Not cheap, but if it reduces your electricity bill by 50%, you are looking at a payback time of about three years. After that, your hot water is free.

Solar geyser

Solar geyser has a payback time of about three years, using an oft-quoted statistic that half the electricity in the home is used to heat water.

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