News24.com | How winter affects solar output in every province in SA

There has been a surge in popularity for solar systems in South Africa given the frequency and intensity of load shedding in recent times.

• Winter climate conditions can impact the output of solar systems. The difference will vary province by province in South Africa.
• In the Western Cape, output may drop by over 50%. Other provinces are unlikely to notice a change.
• There are a few controllable factors for increasing solar output.
• For more stories, visit the Tech and Trends homepage.

With winter months approaching, solar owners, particularly in the Western Cape, might detect changes in the output of their systems.

In the Western Cape, owners can expect solar output to decrease by over 50% whereas in Gauteng, the output is largely unaffected.

This is according to data supplied by Matthew Cruise, the head of business intelligence and public relations at Hohm Energy.

There has been a surge in popularity for solar systems in South Africa given the frequency and intensity of load shedding in recent times.

In the first quarter of 2023, South Africans spent R3.6 billion on importing solar panels, more than three times the amount spent in the previous quarter, according to Gaylor Montmasson-Clair, senior economist at Trade & Industrial Policy Strategies.

A huge solar tax incentive was announced at the national Budget this year, as the government launched a scheme that allows South African businesses to deduct 125% of the cost of a solar project from their tax bill for the next year.

The incentive available for individuals is much weaker as individuals can only claim back 25% of the value of the panels up to a maximum value of R15 000.

Woes for winter?

Cruise said that the output of solar systems is generally lower in winter months for a few reasons.

First, the sun's path is lower in the sky in winter which means that the tilt angle of the panels would need to be higher to perform optimally in winter.

READ MORE | Budget 2023's big news: Eskom debt, solar tax bonanza and tough choices

It would be possible to negate this issue if solar panels were on a racking system, but in most residential cases, the panels are fixed and therefore can't be adjusted.

The optimal tilt angle on a solar panel is between 25 and 35 degrees, but this may be higher in winter, said Cruise.

In addition, Cruise said there were generally more days with cloud cover in winter, resulting in panels receiving less direct sunlight.

Finally, the days in winter are shorter, meaning that solar panels start producing energy later in the day and finish producing earlier.

AWPower said in a blog post that sun rays are more intense in summer when the sun is directly overhead for a larger proportion of the time.

However, there were also some benefits for solar panels output that come from winter conditions. For instance, the efficiency of solar panels decreased slightly at hotter temperatures.

“If you compare a 26-degree day with clear skies to a 36-degree day, you’d see that the panels actually perform better on the 26-degree day,” said Cruise.

“The difference is not extreme but you would see higher output on a cooler day.”

While there was an observable difference between winter and summer solar output in most regions, Cruise said it “isn’t that extreme”. He said that South Africa was one of the best places in the world for solar.

The controllables

Cruise said that there were some factors affecting solar output that solar users could control.

These include ensuring the panels were clean and that there were no objects that could possibly throw shade onto the panels. 

Deciding which direction to face the panels was also important. He said that for Southern Hemisphere countries, it was best to have panels that were north facing as these would generate the most power.

Province by province

A test was conducted which provided an indication of the change in expected output of solar panels for every month in the year for every province.

Cruise said that test was done using the same brand and quantity of panels and inverters, each with a 25-degree tilt that were facing directly north. The only difference was the location the panels were in.

Here is the province-by-province data (no data was provided for the Eastern Cape):

Gauteng

The peak output months for Gauteng are in August and October and the level of output is reasonably flat throughout the year.

Western Cape

The November to January months are the highest output months for the Western Cape - with higher output than the best months in Gauteng. However, solar output in the Western Cape tapers off massively in winter months. There is a 52% decrease in output in June as compared to January.

KwaZulu-Natal

In KZN, output is also reasonably stable, and slightly lower than the best months in the Western Cape. There is an 18% difference between the best and worst output months.

Northern Cape

Production in the Northern Cape peaks in the summer months and comes down 25% in June from the January high.

Mpumalanga

Solar output in Mpumalanga is higher in the winter months than in the summer months.

Limpopo

Output in Limpopo is reasonably consistent with only a 7% spread between the highest and lowest month.

Free State

There is a 17% gap between the lowest and highest months with six months of very strong output.

North West

The output is reasonably consistent throughout the year with peak months between August and October.