Gorgeous Green House

The Renovation Journey of a 1940’s ‘Traditional’ to 2015 ‘Contemporary, Green & Gorgeous’

Solar Geysers vs Heat Pumps: cheap can be expensive!


Eskom (South Africa’s national energy provider) has recently conducted a study comparing solar geysers to heat pumps

Solar geyser

The conclusions drawn from the study were:

  • Heat pumps achieve at least 80% of the savings possible with a comparable solar water heating system, but at far lower installation cost.
  • Heat pumps are a cost effective technology for heating water in commercial applications.

They offer this graph to show the reduced payback period for heat pumps attributing it to the lower installation costs of heat pumps.

Pay back Solar Geysor vs Heat Pump (according to ESKOM)

Pay back Solar Geysor vs Heat Pump (according to ESKOM)

This appears to be a reliable endorsement of heat pumps, but here is what they don’t tell you:

  • Eskom do subsidise heat pumps, but do absolutely no performance testing on them.  Currently there are no heat pumps in South Africa with the SABS (South African Bureau of Standards) mark of approval. In the solar industry, all products on the subsidy programme had to be tested against SANS 1307 prior to being permitted on the programme.
  • Heat pump providers claim they will save you 60% on your water bills.  Possible yes, if every day was an optimum weather day with low humidity and high ambient temperatures.  It is not realist for providers to claim a ratio of the heating provided over the electrical energy consumed (COP) of 3:1, it will average out at 1:1.5.  This assumes you have purchased a quality machine and the large majority of the cheap heat pumps were actually designed as under floor heaters!   To achieve water temperature of 55 degrees the pressure has to be raised from the 18 bar (which it was designed for) to the 38 bar setting.  Making the compressor work at this level is a bit like placing a brick on the gas pedal of a V8.  It’s going to fail!
  • Heat pumps require a sanitary condenser.  This ensures that in the event of a failure no contamination of your water occurs.  When this happens in heat pumps without condensers, the smell of hot oil lingers in the hot water taps.  For this reason Australia and New Zealand have banned non sanitized condenser units, no such restriction are applied in South Africa!
  • Heat pumps are cheaper than solar geysers. Yes, but you still need to buy or connect your heat pump to an electrical geyser and that cost is seldom factored in to the comparison.
  • Heat pump suppliers will tell you that because the sun doesn’t shine at night you will have a cold shower in the morning.  Not true!  A good quality solar system, correctly sized, is designed to supply 24hrs of hot water from 6hrs of sunshine.
  • A final scary scenario to consider:  you purchase a heat pump which fails.  Your phone your insurance company who refute the claim because it in a non- SABS product.  The plumber has disappeared because he bought a container from the east and is getting so many phone calls he’s ‘shut up shop’ and disappeared.  Finally you phone Eskom, as your logic says they’ve provided a subsidy therefore perhaps can provide some sort of relief. They will refer you to point 6 on the subsidy form which states that they take no responsibility for the performance or quality of your heat pump!
polygala virgata

Polygala virgata currently in flower. Beautiful delicate shrub, perfect for urban gardens.

You then go out and purchase a solar geyser!


The South African Mechanical Engineer VOL 62





18 thoughts on “Solar Geysers vs Heat Pumps: cheap can be expensive!

  1. Installed solar geysers two years back. Best renovation choice I have ever made.

  2. Hi,
    You’ve written a nice blog.
    Thank you so much for writing such a wonderful post about Solar Geysers vs Heat Pumps..
    Post is very informative..

    Thanks for sharing such a nice blog…

  3. Great post.. Thanks for sharing information with us.. Keep posting..

  4. Glad you are looking into all of them!

  5. I personally Feel blog, “Solar Geysers vs Heat
    Pumps: cheap can be expensive! Gorgeous Green House”
    was really good! I personallycould not agree with you even
    more! Finally seems like Idiscovered a blog website truly worth checking out.
    Thanks a lot, Alexis

  6. Cheap or expensive, we are still saving other resources, and that’s worth it.

  7. A person doesnt install a heat pump or a solar water heater for a short period. So if you see the long run cost saving its more in solar products and its a renewable resource.

  8. Lisa from PETCO has responded as follows:

    You know, most people don’t as the material gets washed at the recycler in any case as part of the process. Material comes from all over, landfill, manufacturers etc and is in a filthy state. However, from a home perspective, it certainly minimises the odour of your recycling / separation bin at home if your recyclables are washed. I’d continue to wash them, simply put your recyclables next to the sink and use the dish water to do this once you have finished washing dishes.

    Lisa has missed the point about wasting water but does explain that recyclers have to wash ( I assume this would apply to glass and aluminium recyclers). I think to minimize water use its best to just put caps on bottles and containers that have them and just do a swift rinse for other items that may present odour issues. Dish washing machines are very water greedy!

  9. Excellant question. I went to the PETCO website. They are our primary plastics recycling organisation. They have a section called Tips for Recycing but provide no illumination on this issue. I have e-mailed them and will post their response.

  10. Hi Everyone. Thanks for the suggestions on ‘research projects’. Good thing is the holidays so I have the extra time.

    • Laughs!

      Here is another one. Should I wash plastic containers such as milk bottles before putting them in the orange recycling bag? I tried for months to get an answer from Neil Macleod’s office (head of Durban’s Water Department) but without success. So I still don’t know whether I am being a good citizen for washing them, or a bad citizen for wasting a valuable resource (water).

  11. We’ve had a solar geyser on the roof connected to one inside for two years now & save about R600 a month.
    We had a power failure the other day (cable theft!) & I looked at gas fridges & saw they also have solar fridges! Maybe another research project?

  12. I had been wondering about Heat Pumps. Really useful article. Well done. Re Greg’s comment – I know nothing about induction geysers, but induction hot plates are wonderful for cooking.

  13. What about something on induction geysers?

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