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Solar CalculatorProduct Performance Evaluator

Whilst the problem still exists where SABS Mark approval gives no indication that a given product is fit for purpose. As a potential buyer of a solar water heating system, you need the means to accurately evaluate the delivery capability of the various products available on the market. In order to make an informed decision you will need to establish which products suitable for your needs and which will meet you expectations.

With the calculator provided below. This can be done from data listed on the Eskom subsidy web site, since the Rand value of the subsidy is based broadly on Q factor performance measurements.

With this calculator you will be able to compare the performance of different products based on their subsidy value and the indicated capacity of the system.

Product Performance Evaluator
Expected Temperature Graph and Payback Calculator

The calculator works out the Q factor of the system from the subsidy value, the capacity of the systems and the rand value multiplier used by Eskom.

It further provides an indication of the products ability to deliver a 40oC temperature rise in the volume of water specified as the system capacity. This is indicated as a “percentage of energy required supplied from solar input.”

The calculator also offers a measure of the cost effectiveness of a system based on its ability to displace electricity consumption and arrives at a cost per kilo watt hour for the capital cost to purchase the system.

In our opinion any product delivering less than 90% of the required energy, as measured in SABS testing, can at best only be considered a supplementary system;. whereas a product capable of delivering 90% and above will be able to provide a useful amount of energy all year round. This makes it a better value proposition as it will be functionally superior and more quickly be able to deliver a return on investment.


What performance level should be expected as a minimum?

In an analysis conducted on the data listed on the Eskom website we have observed that approximately 40% of the products listed as being available under subsidy, deliver less than 60% of the energy required to achieve a 40oC temperature rise from solar input at the SABS test datum of 16MJ of solar insolation. This is alarming as it means that many of the systems being offered still require a considerable amount of electricity input to bring the water up to temperature.

With the public being lead to believe that 40% of electricity consumption is attributed to water heating it is our concern that buyers of such low performing systems will not see the energy savings they were expecting.