sustainable.co.za online calculator launched (and reviewed)

Submitted by turbosprout on Thu, 2011-01-27 14:19

sustainable.co.za calculatorsustainable.co.za calculatorI've been looking forward to the launch of sustainable.co.za's online calculator since I first heard that it was in the pipeline a few weeks ago.

Online calculators of the carbon variety have been around for quite a while and vary in their suitability to the SA energy scenario and ease of use. It seems like quite a tricky piece of software to nail down properly and I still think there is room for SA's carbon calculators to improve.

That said, the sustainable.co.za calculator is a bit different to a carbon calculator. It measures how much electricity you can save by calculating the energy expenditure of your old high-consumption lighting and water heating fittings/appliances and suggesting eco-friendly replacement options. So it's not measuring your carbon or overall ecological footprint but specifically looks at your electricity use and highlights the products that you could purchase from their online store to save you energy (and money).

The calculator has an easily usable interface and does what it says, quickly. You put in your average electricity expenditure and select the current (non-energy efficient) products you want to look into replacing.

It can be used to provide a forecast of Eskom rate increases and shows what your electricity is likely to cost in years to come. At the moment (summer) our household spends around R 200 on electricity a month (thanks to our energy efficiency measures and a bit of free electricity from the City of Cape Town ;-). With the projected Eskom increases, according to the calculator, this will cost R 390.63 by September 2013. And will hit R 1235.53 by Jan 2021. Obviously this is a bit of crystal ball gazing, but illustrates the point: significant electricity price hikes are likely to be a yearly phenomenon.

Tip: to see what your monthly bill is likely to be in future put in your amount and before adding any products, select the [Show / Hide detailed Calculations] button in the bottom right. This then shows a timeline of your future electricity bill before any cost savings are taken into account.

Then you can select your current lighting (different wattage bulbs) and water heating products (geysers, shower heads) in use in the home and see what sustainable alternatives are available for purchase.

I decided to do a quick audit of our home lighting to see if any improvements could be made that make sense ecologically and economically. I found:

  • 18x Compact Fluorescent bulbs (Cfl)
  • 10x 50W Halogen downlighters (passage, bedroom)
  • 1x 150W Outside flood light (not in use)
  • 1x 300W (two bulbs) Outside flood light (with motion sensor)
  • 1x 150W Halogen outside light (with motion sensor)
  • 1x dual fluorescent strip light in garage
  • 1x single fluorescent strip light in shed
  • 1x 60W Incandescent (eek, an old outside light that has an opaque cover!)


Using the tool I sussed out what the halogen downlighters would cost to replace. The tool suggested a 5 Watt Ecolux downlight (amazing that 5W LED provides equivalent lighting to 50W of Halogen) that retails at R 295. As these downlighters are used very infrequently (less than 5min a day) the payback period on the cost to replace all ten will exceed 10 years and the monthly saving would only be about R 1.

If however these halogen downlighters were in a small shop operating for 8 hours a day, replacing them with the suggested equivalent would pay for itself after 1 year and 10 months and thereafter save R100 a month (at today's energy prices). So in this scenario it would make sense to invest R 2950 in the lighting.

If you are using outside floodlighting for security the best option is to use a motion sensor so that the lights are only on for a short period of time. If however you need constant outdoor illumination its interesting to know that 30W of LED can provide the equivalent lighting of a 300W floodlight. According to the calculator, operated at 10 hours a day, it would payback the R 2553 it cost by savings in electricity in 2 years and 1 month. (It would actually be shorter as the light would be on longer in winter).

A limitation of the calculator is that it only suggests equivalent LED products for lighting. So if for example you are still running 60W incandescent light bulbs it will suggest replacing these with 6W LEDs which are still a bit pricy for general use at R 266 each (better environmental benefits over Cfl but price is still a factor for most). I guess sustainable.co.za doesn't sell common Cfl's (no point when you can buy them at shopright!) but would still be nice to include these Cfl figures for comparison.

It would also be good to see some of the assumptions the calculator uses when it comes to the savings calculations. E.g. when choosing a low flow shower head, what average litre/minute figure are you assuming the existing (non low-flow shower is using)? Number of minutes in operation, what percentage of the water is heated (some people like warmer showers than others, others shower with a friend...)

Emailing you the calculations is a great feature so that you have a copy of the details in your inbox. Here it would be useful for sustainable to include the number of hours you selected in your scenario in the email too.

Overall I think this is a good tool that pushes the envelope a bit for SA environmental online calculators. Lets hope we see more.

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