How to get the best out of solar in South Africa

 ·21 Oct 2023

With load shedding not going anywhere anytime soon, many households and businesses are turning to solar energy, but several matters must be considered.

According to Teresa Kok from One Energy Group, with the sharp increase in electricity prices to beyond R3.50 kW/h and increasing exponentially year-on-year, obtaining the best return on your solar investment should also be a critical objective.

“It all starts by getting a thorough electricity usage and needs analysis done to determine the best system design to ensure that not only do you have enough backup when you need it for power outages. But that your system can equally generate and supply enough power to reduce your grid electricity usage and cost as much as possible,” Kok said.

With this in mind, One Energy gave eight tips on how to get to scale a solar PV system to get the best returns:

Match Demand with Supply

Analysing electricity usage will show when peak electricity demand is reached and how much each circuit uses.

With this data, one can design a system that generates as much energy as they normally use.

This will also allow one to look at which systems have the most usage, allowing them to reconsider the time and duration of usage of a product.

Get the best Panels

Although having an inverter can shield one from load shedding, there is no saving on electricity costs without solar panels.

“For businesses where your main electricity consumption happens during daylight hours, which is also when the sun is supplying the bulk of your electricity needs, this is an absolute win,” Kok said.

“When selecting panels, invest in the highest-grade monocrystalline panels you can – premium efficiency translates directly into better energy output and savings over time.”

Although many municipalities allow excess solar to be fed back into the grid, many feed-in tariffs and an expensive update to one’s electricity meter mean that it is not worth spending money on a larger PV System.

“For now, the best savings you can make is by storing your excess generation in a bigger battery bank, and then using your own energy when you need it. Your best option remains to get as close to 90% or more of your electricity usage coming from self-generation,” Kok said.

Add Battery Storage

Using a better storage system will ensure that one completely shields themselves from soaring electricity costs, with extra power generated through solar energy diverted to charge the batteries.

This will ensure that one has power even during cloudier days or grid outages.

“If you have enough battery capacity and your system is programmed correctly when your property starts to draw from the grid when the sun goes down, the battery will step in and supply the energy saved in your batteries from earlier, instead of you drawing from the grid,” Kok said.

Lithium-ion phosphate batteries

Although Lithium-ion Phosphate batteries are seen as expensive, Kok said that this is not true when one looks at the average cost per kW over the life of the battery.

She looked at the following costs for a 5kW battery that costs R30,000:

  • With a Depth of Discharge (DOD) of 80% (ie 80% of usable capacity,, which is a protective mechanism to extend the lifespan of your lithium-ion battery) – therefore 4kWh usable power per cycle.
  • Battery lifespan = 6000 cycles
  • Total power over the life of battery = 6000 cycles x 4 kWh per cycle = 24000 kWh
  • Average cost per kWh = R30000 / 24000 kW = R1.25 per KWh.

This is far lower than the residential cost of R3.51 per kWh (Ekurhuleni tariff B) charged by Eskom.

“Your strategy should be to cycle the Lithium batteries and increase the battery capacity to maximise the installed inverter and panel array capacity as close to daily electricity consumption as possible. Every kWh of solar electricity generated is another knocked off your electricity bill,” she added.

A quality hybrid Inverter is key

The inverter for a solar system is key to getting the best solar return on investment (ROI). Kok recommends a reliable hybrid inverter with a 10-year warranty.

“One of the key issues with cheaper, ‘off-grid’ inverters is that they are unidirectional so the solar power can only address the essential services circuits, and savings cannot be made on the higher load items that are not on the backup side of the distribution board (DB),” she said.

“More sophisticated hybrid inverters are bidirectional, so they allow savings both upstream and downstream of the inverter, drawing power from both the grid and battery storage in a coordinated exercise to maximise the power you use from self-generation, and only drawing from the grid when it’s absolutely necessary.”

Cheaper off-grid inverters will also go completely to grid power if the load exceeds supply, meaning that one’s solar is not used at all.

Geyser switch

Electric geysers usually use between 30% to 40% of one ‘s monthly electricity usage and cost, and making the switch from electric to solar geysers can make a substantial difference.

For instance, on a R3,000 electricity bill, one will save roughly R880 per month, amortising the outlay in slightly over two years.

Calculating the Solar Payback Period?

The “solar payback period” is how long it takes one to recoup their initial investment in solar.

Although this varies due to peak sunlight, solar array size, and other factors, it will generally take 5 to 7 years for homeowners to break even.

It is calculated through the following: Initial system cost / annual electricity savings = payback period. (Break-even)


ROI looks at the solar buyback period and calculates the amount of money and savings that a PV system will provide over its lifelines and the expected utility costs over the same period.

For instance, for an electricity bill of R2,450 per month, a system would look like this:

  • 5kW Inverter
  • 10kWh li-Ion batteries (upscale your batteries for reasons explained earlier – it’s cheaper per kWh than Eskom/council) 
  • 4.3kW solar panel array

According to Kok, the fully installed price with all materials and COC comes out to R148,000.

On an upfront purchase: based on the 18,65% electricity tariff increase this year, the 12,74% for next year, and a conservative 5% estimated to increase the following year, it will take 5.5 years to break even.

One’s cumulative saving on electricity costs will then be R350,000 after ten years and R940,000 after 20 years – resulting in a savings multiple of 6.3 on the original investment.

On a finance option based on prime interest rates with a finance term of five years with no escalation, one’s monthly repayment would come to around R3,580 per month (depending on one’s credit rating).

The monthly savings are roughly R2,200 in the first year, which will then grow, as does the cost per kWh of grid electricity.

“Your system will be fully paid off in five years (60 months), and you will own it, and for the rest of the 15-20+ years of your system lifespan, you will be generating your electricity for free, with less than a 10% reliance on grid electricity,” Kok said.

Read: South Africa’s R660 billion electricity problem

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