SA supermarkets spend US$1bn on diesel for power

During the latter part of 2022, the country’s two largest supermarket groups – Shoprite and Pick n Pay – spent a combined R906 million on diesel for generators at stores. Woolworths spent R90 million (primarily at its Food stores), taking that total to R1 billion*.

This is an astonishing number across roughly 3 000 grocery stores in South Africa, and one that was concentrated in the last few months of the year where elevated levels of load shedding (above Stage 4) were in place practically continuously.

The most common retort to this is ‘Why don’t retailers just install solar?’

After all, a handful of rooftop solar photovoltaic (PV) panels, a modestly sized inverter and a battery or two will keep the household essentials running during load shedding.

If only it was that simple.

The first complication is where the supermarket is located.

For supermarkets inside large (and even ‘biggish’ malls), the available rooftop space is owned by the landlord. 

At centres where conditions are ideal (large, flat roofs in regions of the country with lots of sunshine), these property owners have generally already installed solar.

This energy is being used to supplement Eskom/municipal supply, and the power generated is not enough to power the entire centre for the entire day (24 hours). Most installations don’t have battery components. Landlords typically consider these installations the same way they would any other capital investment: what is the return on investment? (Payback is easily under 10 years currently). – Bloomberg

For those mostly older properties where roofs aren’t ideal, these calculations likely don’t (yet) make sense.

If a supermarket is in a neighbourhood-type centre (some of these are owned by the various retailers, like Shoprite), the investment decision is somewhat simpler. Also, power needs in these kinds of centres tend to be lower but this is dependent on tenant mix (a row of fast-food outlets will see the average consumption per square metre soar).

But the roofs in these centres are too small to have a solar installation power the entire centre. One of Shoprite’s own flagship projects, at Sitari Village Mall in Somerset West, solar PV (the entire roof is covered) is only enough for 35 percent of the centre’s needs.

The remaining 65 percent is from wind power (using Eskom’s Renewable Energy Tariff programme). Theoretically, it is ‘wheeling’ power from wind farms across its grid.

Battery backup?

A further obstacle is that electricity from solar PV is not dispatchable. When the sun shines, power is produced. When the sun doesn’t, there’s no power.

In a household scenario, batteries are used to store power produced during the day for the evening peak.

    This could be a solution, but if solar cannot even provide half the requirements of a shopping centre anchored by a brand-new, energy efficient Checkers store, where is the energy to bank?

Even in an almost-perfect scenario, the new Builders Warehouse in Midrand – a giant rectangular warehouse with optimal space for solar – PV cannot provide 100% of the store’s daily power requirements. It hits that mark during the “middle part of the day”, but on average solar delivers 70 percent of its power requirements.

Solar-topped carports could be installed in parking lots to boost output and this will continue to happen at shopping centres and stores (like Makro outlets) where the investment cases make sense.

But a building supplies store is not a supermarket.

Its power consumption profile is vastly different. Chiefly, there is no cold chain. In that Builders store, cooling/heating (air conditioning) is likely the biggest consumer of power. There is no refrigeration, no freezers, no ovens.

A recent UK government report estimates that refrigeration systems account for 30 percent to 60 percent of the electricity used by a store. Food retailers have been driving this down, but have also shifted to energy-efficient lighting and HVAC (heating, ventilation and air conditioning) systems.

Refrigeration tends to remain the biggest consumer of electricity in supermarkets.

Wonder why new Wooolworths stores have doors on their fruit/veg, convenience food and meat fridges? And why Checkers and Pick n Pay have all but abandoned open-top freezers in favour of upright ones with doors?

The cold chain is paramount. If the Woolworths cold chain is broken for more than eight consecutive minutes, it removes those products from shelves and gives them to food charities. At rivals, the number is about the same.

Listen/Read: Woolies reports biggest ever first-half profit

This means that when load shedding kicks in, supermarkets have to switch to dispatchable power immediately to ensure that any interruption is, at most, a minute or two.

The cold chain also has to be in place 24 hours a day, including overnight when stores are not trading.

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