The big problem with inverters and battery backups in South Africa –

South African households that cannot afford a full transition to solar energy – or may be limited by body corporates and other logistical issues preventing them from going solar – are increasingly turning to inverter and battery back-ups to keep the lights on during load shedding.

However, energy experts have warned that while these solutions may be a way to prevent being left in the dark during outages, they do not help Eskom and South Africa resolve the energy crisis. In fact, they make things worse.

According to energy and technology firm Rubicon’s Dylan Schnetler, inverter and battery backup systems have proven to be vital for many households and small businesses to keep power outages at bay – boosting economic activity and allowing a degree of normality.

But if these backups are not fed from independent energy generation sources – such as solar – the system is still drawing all its power from the national grid – it’s just delayed.

Once load shedding ends, the battery system usually automatically starts recharging; when this is combined with the normal draw from the household, the system effectively doubles the demand on the grid.

“While battery backup systems provide temporary relief during power outages, they still rely on Eskom for recharging, which inadvertently adds to the burden on the already strained power grid. To genuinely support Eskom and tackle the energy deficit, it’s crucial for households to generate electricity independently,” Schnetler said.

“After a power outage, when the electricity comes back on, the batteries immediately start recharging while the household is also drawing power from the grid. This double power consumption may exceed the capacity of local electrical networks, causing them to trip or – in a worst-case scenario – damage them.

“This then requires the local municipality to send personnel to restart or repair the substation, leading to further prolonged power outages for all the power users in the same area,” he said.

The problem of inverter/battery combos not benefitting South Africa’s energy generation is a key reason these items are not covered by the solar tax incentive for individuals – while the ‘double draw’ issue has also been flagged by researchers as a significant problem for the grid.

In 2023, a study on the impact of inverters and batteries in South Africa was done, where it was found that battery charging can undo approximately 85% and 90% of load shedding in summer and winter, respectively, by increasing demand on the grid after scheduled outages.

At just a 25% penetration rate (ie, 25% of households using this system), the objectives of load shedding are effectively reversed.

To counter this problem, the researchers suggested that power utilities find a way to limit or otherwise restrict the charging of batteries from the grid.

Schnetler said that an option for homeowners is to use technology to control their inverter so that it doesn’t immediately draw power from the grid to recharge the batteries as soon as the load shedding period ends, but rather waits for an hour or so.

“Correctly configured, this still gives ample time for the batteries to recharge before the next round of load shedding, without putting additional strain on the grid right when the electricity is restored,” he said.

However, the best option is still to recharge the batteries using solar energy, reducing the dependence on Eskom’s power entirely, he said.

Read: Treasury clears up confusion over tax breaks for solar, batteries and inverters