A dummy's guide to load shedding


News that Eskom had instituted stage 2 load shedding on Wednesday – at short notice – had South Africans scrambling to find the latest power cut schedules for their municipalities and cross-referencing tiny block codes denoting suburbs with tables containing times when electricity would be out.

Despite South Africa experiencing intermittent power outages for over ten years, government has still not designed a national search function where South African can easily enter their town or suburb and find out when they will be without power.

The private sector has since stepped in, and usage of the popular app Eskom se Push - which sends you localised load shedding alerts - has exploded. Earlier this year, it had 400 000 active users.

To understand how and why the load shedding system works the way it does, some background is needed. 

1. What is load shedding?

Eskom institutes rotational power outages when its engineers fear that demand may exceed capacity. They are trying to avoid at all costs a national blackout caused by a severely overburdened grid. This could lead to a grid collapse, and no electricity at all for large parts of the country.

While the utility, on paper, has more than enough capacity to meet demand, it has been battling severe capacity shortages for well over a decade.

These occur due to unplanned plant breakdowns, often coupled with other generating units being offline for planned maintenance. As the difference between demand and supply begins to shrink, Eskom fires up emergency power generators to create electricity using expensive diesel, and may request big users to start cuts. 

Load shedding is what happens when Eskom proactively decides that emergency measures are not enough, and demand must fall further so that it does not near the danger zone of a grid collapse.

2. And then? 

There is no central committee room at Eskom where stressed engineers mull over which areas to switch off. While Eskom sells electricity directly to some users, it mostly sells power to municipalities. The municipalities then sell on the power to users at a slight mark-up.

And the power utility does not tell the municipalities which areas should be load shed at which times.

Rather, it puts through a demand to all municipalities in the country to meet the load shedding requirements. It is then up to the municipalities to decide when and where to cut power.

3. So each municipality that sells power to its residents plans how to cut power?

Yes. And, broadly speaking, the larger the municipality, the more complex it becomes.

All generally use the same three-step process for planning purposes.

First the municipality is divided into different blocks – more or less the same number of residents – which can contain multiple suburbs. 

Second, each block is given a code – usually a number, or a letter, or sometimes a combination. Multiple suburbs can fall within these block codes.

Third, tables are published (in theory, proactively shared with residents) showing which blocks will be without power, at which times, on which day of the month, under which circumstances.

Now these tables have to be created for each stage of load shedding, and there are eight in total. If that isn’t confusing enough, some municipalities change the tables monthly, or at other intervals. Others keep them the same to assist residents.

In all municipalities, however, the time that load shedding takes place changes daily for the different blocks. Why? Because there are slightly better and worse times to be without power. No-one wants to be without electricity between 06:00 and 08:30 when kids have to be made ready for school and breakfast made.

The result, then, is a nationwide system of hundreds of different load shedding schedules than make Babylonian lunar calendars look like a piece of cake. 

There is also a slight chance that your municipality is not load shedding at the same stage as Eskom has announced. Cape Town, for example, due to some spare generation capacity, is often one stage behind national load shedding. (It may be at stage one, for example, while the rest of the country is at stage two.) 

4.  So how do I find out whether I will end up in the dark? 

Let's say you live in Rosebank, Johannesburg. As a City Power Johannesburg customer, you know that you will have to consult your municipality for your schedule. 

You go to City Power's website and you find that there are links to 16 PDFs named 1A to 8B. These are the lists of which suburbs fall within which load shedding block. You find that Rosebank is in block 1A.

Next, you hunt down the load shedding table, which City Power calls its 'operating schedule' (municipalities may have different names for this). 

You then check the day of the month, the time and the load shedding stage. You'll find that, on Wednesday, October 16, you will be load shed between 20:00 and 00:30 if stage 2 load shedding remains in place. Easy. 

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