Here you’ll find answers to all of your most commonly asked questions.

Elon® FAQ

How can solar PV water heating be more cost-effective than solar thermal? Isn’t solar thermal efficiency much better than solar PV?

It is true that solar thermal collectors are currently more efficient per square meter (area) than solar PV modules in collecting solar energy. However, overall efficiency must also take into consideration factors such as heat loss in piping (especially in winter) and energy use of solar thermal circulation pumps.

Solar thermal system lifetimes range from about 7 years (for cheap imports) to about 15 years for high quality (and more expensive) systems. (In a comprehensive analysis, Sandia National Laboratories found that about 50% of solar thermal systems fail within a 10-year period.) Solar PV modules are routinely guaranteed at 80% performance after 25 years, and the US National Renewable Energy Laboratory uses a lifetime of 33 years in its solar PV system calculations.

Solar PV module costs have dropped dramatically – by over 80% in the past 5 years – and the trend is continuing. This has changed the paradigm. Whilst solar PV systems will continue to require more roof space than solar thermal in the short term, the key issue is not roof space, but cost. Solar PV systems have become cost-competitive to solar thermal, and the much longer lifetimes and lower maintenance translate into a lower lifetime cost per kWh.

What is SANS 10400-XA?

It is a set of energy efficiency regulations that are compulsory for new buildings and for additions and extensions to existing buildings. One of the key requirements of SANS 10400-XA is that no more than 50% of the annual volume of domestic hot water must be heated using grid electricity.

The PowerOptimal Elon® makes meeting this requirement easier than ever before, providing a new cost-effective alternative to heat pump and solar thermal systems.

Do I need to change the heating element on my existing geyser to install a PowerOptimal Elon® system?

Not necessarily. PowerOptimal Elon® works with existing standard AC heater elements, but the best element size (power rating) depends on the size of your solar PV array. If you are building a new house, you can just specify the right heater element from the start. Refer to the Easy Selection Guide on the Downloads page or ask the PowerOptimal agent or your installer about the best solar PV module & heater element matching configuration for your needs.

How many solar modules do I need?

The most important factor here is the total size or power of the solar PV array (measured in kilowatt or kWp) rather than the number of modules. We recommend a minimum of 1 kWp.

The size of solar PV array required depends on the number of people in the household as well as your hot water usage levels. Below is a basic guide. Refer to the Elon® 100 Easy Selection Guide on this page to download the basic guide or the Elon® 100 Solar PV Array and Heating Element Selection Guide on this page for a more detailed guide.

* 6-minute showers at 40 °C with 8 litre/min (low-flow) showerhead

What is the most cost-effective water heating option in South Africa?

To understand the full cost of any water heating solution, you have to consider several things: the upfront (capital) cost, the ongoing (operating) cost, the maintenance cost as well as how long the solution will last before you have to replace it (lifetime). Otherwise you cannot do a proper comparison.

The full cost of energy that considers ALL cost components well as the  lifetime is called the Levelized Cost of Energy or LCOE.

When comparing South African energy options including grid electricity, solar thermal (solar geysers), heat pumps, gas and solar PV, the Elon® is the most cost-effective of all the options. See the full results and methodology here (click on the “Levelized Cost of Energy” tab).

What is the payback period for an Elon® system?

This depends on your current electricity tariff, how many solar modules you install, your hot water use, and electricity price increases in the next few years, but typically payback period is in the range of 2.5 to 5 years. With a typical solar module life expectancy of more than 30 years, this means that you will enjoy at least 25 years of free hot water!

See the Case Studies page for more performance information.

Where can I learn more about the PowerOptimal Elon®?

Explore the website (see for example the case studies page and the downloads menu item) or contact the PowerOptimal team for more information.