July 6th, 2011 by Tim Leave a reply »

It has always been our intention to install either solar and or a heat pump geyser, the main motivation being to try reduce our carbon foot-print. I have however long maintained that claims made by industry regarding the potential savings and payback periods on equipment to be optimistic in the least.

It is not uncommon to see claims of payback periods of 2-3 years and electricity savings of 40 % in adverts for solar or heat pump products, but I simply didn’t buy this. So rather than dive right in I decided to to put an electrical meter onto the geyser so it could be monitored separately. I have been doing this since August 2010 and feel I have enough data to make a few assumptions to refute some of wild claims made by some of the installers.

But first our set-up, which I consider a reasonably average:

  • House is a brick and tile house, 3 bedrooms
  • Family of 4, kids share a bath daily, parents shower at least once daily
  • Geyser is a 100L element type inherited with the house – no pipe lagging or geyser blanket.
  • Temperature set on highest (70 deg) or else we run out of hot water in the morning.
  • We use gas for most of our cooking which will reduce the total usage, pushing geyser percentage higher.

Other things to consider, we are currently under water restrictions, but through clever water management (see rain water/grey water elsewhere on my site) we have been able to maintain the luxury of decent length showers and baths whilst still doing our bit.

So here are our figures, I have inflated them to include the latest tariff hike of July 2011 (R1.05 / kWh)

So what does this mean ?

Well for one thing we definitely don’t even come close to using 40% of our bill on heating water, secondly even if we managed to eliminate the total geyser bill this would only save us about R310  / month (was R203 prior to this month’s increase).

So even with Eskom rebates you only going to break even after 5 years at which point you will probably need to replace the old system (assumes R17 000 outlay, financed).

I think my point is don’t believe everything you’re told and be especially suspicious of mates who claim their bill has halved since installing their solar geyser unless they have documented the before and after scenarios . I realise that everybody’s situation is different  and this needs to be taken into account, I think however manufacturers must be using some rather extreme case studies to punt their products (well that’s nothing new is it?)

I am going to wait a year, by then Eskom would have hiked prices again, I think there will be more competition and the rebate issue might have calmed down (that’s another whole post – suffice to say I believe you ending up paying more with the rebate than without). In the meantime I am adding lagging to the pipes in the ceiling this weekend to see what a difference this will make. I’ll keep you posted.



  1. valenshki says:

    i would be interested to know where you stand on this topic now, a year later?

  2. Antonius says:

    Tim, thanks for the post. I have been considering solar energy for a while but the math dit not make sense (I am not an engineer). Yes, industry make claims and add a % (what % I might add….30-300%). Just like the effectiveness of LED lights (which I doubt), you need some guy to test the actual product under actual conditions no matter how many rooms or children you have, at least there is a bench mark where there was’nt one before. Great work, keep it going. Antonius

  3. Jane says:

    Thanks for this – another factor to count in is the cost of the maintenance of a solar geyser. They have to be serviced every year otherwise the warrantee is void. The cost of that works out to be about a month’s worth of pre-solar electricity. In our calculations, it worked out that it would take six to eight years before we started seeing any savings. We will probably not even be in this house then!!

  4. Erik Groothuijzen says:

    Hi Tim,
    I fitted a solar panel to my original Kwikot geyser with a solar driven 10W pump. Very simple, no maintenance. The sun shines, the pump circulates. I agree with your % electricity savings and additional lagging and a geyser blanket also helps. When I was working and my wife and I had a regular life, I also fitted a Geyserwise, basically heating up the water when we needed it i.e. two hours in the morning before work for a shower and one hour in the evening for cooking and dishes with the temperature set to 50 degrees. These days I only rely on the panel for hot water.

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