South Africans can say goodbye to Eskom for less than ever before
South African households can go off-grid much more cheaply by focusing on reducing their electricity demand for heating, cooling, and cooking rather than increasing the size of their solar power system.
Eskom and several municipalities have drastically increased fixed electricity charges in recent years, making energy substantially more expensive for homes that only make sparing use of the grid.
That includes many homes with solar power. Before the radical increases in fixed costs, installers like Alumo Energy typically designed systems that met 80% to 90% of a household’s demand.
They assumed the grid would step in to cover the remaining 10% to 20% during prolonged rain, intense winter cold snaps, or when people accidentally ran power-intensive appliances simultaneously.
The substantial increases in fixed capacity fees have altered the formulas for achieving an optimal balance between self-generation and grid usage to keep total energy costs as low as possible.
For many households that have already invested in solar power, the best option from a cost perspective might be to go fully off-grid to cut their utility connection and avoid fixed charges entirely.
However, going fully off-grid will require more than another 10% to 20% of panel or battery capacity to account for the lack of utility power.
Photovoltaic solar panels can drop to well below 10% of their ideal production potential on days with thick cloud cover.
For many households, increasing the array’s capacity 10-fold is not possible due to space constraints. With such a large number of solar panels, inverter limits are also a major factor.
Therefore, installers use a combination of panel and battery oversizing to maximise system running days. The cost of that system is about double to triple that of an 80% to 90% self-sufficient system.
Alumo Energy provided example quotes showing how much households with four levels of energy consumption from 450kWh to 1,200kWh will pay.
The costs ranged from roughly R175,000 to R317,000, although Alumo stressed that component prices and ideal system configurations could vary greatly.
Fix the demand, not the supply
A cheaper option could be to plug the shortfall in generation and stored energy with a fuel-powered generator. However, this is not allowed by many homeowners’ associations and body corporates.
Another way to minimise the cost of an off-grid system is to make the home more energy-efficient, which can reduce the required size of the inverter, panels, and batteries.
Alumo Energy told MyBroadband that standard resistive element geysers were solar “killers,” as they could consume up to 40% of a household’s electricity demand.
To take this impact out of the equation completely, households can switch to a gas-powered geyser to provide hot water on demand.
A second option is to install a geyser timer to turn on water heating at a time when the batteries are fully charged, so the solar panels can provide the energy needed.
“Geyser controllers can switch geysers on or off for a specific amount of time and keep them at specified temperatures,” Alumo Energy explained.
“You can program the geyser to switch on between 10:00 and 15:00, set your desired temperature so that when you are back home in the evening, you have hot water ready,” Alumo Energy said.
Some switches also support Wi-Fi connectivity, so that users can remotely control appliances to switch on during the day.
Alumo Energy recommended CBI’s smart Wi-Fi timers as its experience in the market had shown these to be of a high quality, while offering great value for money.
The company also pointed out that electric stoves and ovens were energy gluttons, especially in terms of instantaneous power consumption.
“An electric oven or stove draws massive spikes of power that force you into buying larger, more
expensive inverters,” the company said.
Alumo Energy proposed gas hobs and stoves as an alternative. Many households have also turned to more energy-efficient cooking appliances — such as air fryers — to reduce their energy use.
Homes with old air conditioners should also consider replacing them with more modern inverter-integrated models.
These can reduce electricity consumption by as much as 50% with dynamic power draw rather than stop-start systems.
They also feature “soft start” technology that prevents significant voltage drops that could trip off-grid inverters.
Lastly, Alumo recommended that homes with pool pumps put them on timers to run exclusively during the mid-day hours — typically 10:00 to 15:00 — when solar production is optimal.
“This ensures it runs entirely on ‘free’ live solar generation when your batteries are already full, rather than draining your battery bank at night.”
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