Kissing Eskom goodbye got much cheaper

A solar power system large enough to take a typical South African home 100% off-grid costs between R143,000 and R381,000 in July 2024, substantially cheaper than at the start of the year.

Solar power installers have seen a plunge in demand for their products and services due to a significant reduction in load-shedding in the first half of 2024.

However, Eskom’s plans for future electricity tariffs could reinvigorate the industry with households seeking to cut themselves off from the grid completely and avoid higher fixed charges just for having a connection.

Multiple solar power system installers have previously told MyBroadband that going fully off-grid is substantially more expensive than getting a grid-tied system that can meet over 90% of a home’s needs.

The reason for this is fairly straightforward — a fully off-grid system cannot tap into the grid during prolonged periods with little solar generation — like a week of cloudy weather.

MyBroadband used Solar Advice’s configurator to determine the cost of a truly off-grid solar power system for households with varying usage levels.

For the maximum inverter output, we used 10kW for smaller households and 15kW for larger homes.

This would be more than suitable for running even the most power-demanding appliances in most instances.

In terms of solar panel arrays, we used an “oversize factor” of 2.5 on the monthly production. This number was based on solar installers recommending oversizing by two or three times the regular required capacity.

This will help the system charge the batteries as close to full as possible, even during periods with little sunshine.

The same oversize factor was applied to the batteries, although it required a more complex calculation.

Typically, South African households can rely on direct power from their solar panels on most days. The key time of the day when batteries come into play is at night.

Therefore, we also configured the battery storage to be 2.5 times greater than the typical demand at night, which we assumed was 60% of the total daily demand.

The table below compares how much it would cost to go off-grid for households with 450kWh, 600kWh, 900kWh, and 1,200kWh of monthly energy consumption.

When MyBroadband previously calculated off-grid system costs, we found the prices for similar systems to those above would be between R224,492 and R528,637.

The price of the entry-level system has dropped by R45,756 — or about 20%. On the top-end system, the new price of R380,993 is roughly 28% of the previous price of R528,637.

It should be noted that the systems above will be capable of generating far more electricity than your home can consume, and there will be nowhere else for that energy to go.

Therefore, households in municipalities with feed-in credits, like the City of Cape Town, will miss out on potential payouts for additional power.

A little bit of combustion

Integrating a fuel-powered generator into your home’s electricity supply is a more affordable upfront alternative to a vastly oversized system relying solely on solar and battery power.

The two major downsides to this setup are that you must pay for the petrol or diesel you consume, and generators are generally noisy while operating.

In addition, generators may have some load limits that prevent them from running at peak capacity constantly and must be serviced regularly to ensure safe and efficient operation.

However, it can significantly reduce an off-grid system’s initial upfront capital outlay because a generator can replace the extra solar power system capacity at a fraction of the cost.

The table below shows how much off-grid systems supported by fuel-based generators will cost for the same usage levels in our previous comparison.