Loadshedding-Induced Transients Due to Battery Backup Systems and Electric Water Heaters

What happens to Eskom’s domestic load when electric water heaters (geysers) reheat and battery backup batteries recharge after bouts of loadshedding? In this research, Doctor Michael Ritchie and Professors Japie Engelbrecht and Thinus Booysen investigate this question as well as how solar power provision to the household load and to the water heater mitigates this impact. 

In their research, the authors present a simulation of a substantial group of South African residential households to analyse and determine the collective electricity usage. They assess the impact of loadshedding on the grid and the effect of backup batteries and electric water heaters (EWHs), both with and without the integration of storage-less PV installations.


Loadshedding is a persistent reality in South Africa for over, impacting households for hours each day. This intentional disruption of power supply aims to prevent a total grid collapse when demand outstrips supply, a situation largely attributed to Eskom’s aging coal-fired power plants and lack of investment in new capacity.

Loadshedding is a systematic, rotating interruption of electricity across the country, impacting households, businesses, and essential services alike. The higher the loadshedding stage, the more frequent and prolonged the power cuts become.

While affluent households have turned to battery backups as a solution, this approach, without solar power, can hinder the electrical grid’s stability. While providing temporary relief, this approach can inadvertently increase grid demand when batteries recharge after loadshedding, undermining the intended load reduction.

A more sustainable solution involves solar power, which can offset the demand for electricity, particularly during daylight hours. When paired with battery storage, solar can significantly reduce the need for loadshedding, especially during peak summer months.


Fig 1: The escalation of loadshedding since September 2022

Research Results

The growing popularity of battery backup systems is complicating South Africa’s loadshedding crisis. While these systems offer temporary relief during blackouts, our research reveals a significant drawback when they’re not paired with solar power: recharging them after loadshedding can actually increase demand on the grid, counteracting the purpose of the power cuts.

In contrast, homes with solar-powered batteries tell a different story. Excess solar energy can dramatically reduce the need for loadshedding, especially during summer daylight hours.

Based on these findings, we recommend reconsidering policies on battery backup systems. Limiting or even banning charging from the grid during peak hours could be necessary. To ease the financial burden this could cause, we also advocate for time-of-use billing and peak demand tariffs, incentivising off-peak energy use.

Ultimately, we urge a greater focus on integrating solar power with battery systems. This approach offers a sustainable solution that not only eases the strain on the grid but also contributes to a cleaner and more reliable energy future for South Africa.

You can download and read the complete research paper at https://www.sciencedirect.com/science/article/pii/S0306261924008043?via%3Dihub#sec4