**Notes: the figures in this article are estimates. If you are shopping around, make use of our solar calculator here. And for a tailored quote, get in touch with our team of engineers at info@awpower.co.za
There is a monumental difference in the price you would pay for a solar power system capable of providing around 95% of your electricity usage compared to one that can achieve 100%.
AWPower’s managing director, Christiaan Hattingh, told MyBroadband in an interview that, for most households, he would strongly advise against an entirely off-grid solar energy system without Eskom as a backup.
Hattingh explained that going off-grid means oversizing a home’s solar power system to ensure it can meet the household’s electricity demands during cloudy periods.
When it is overcast and raining, generation from photovoltaic (PV) solar panels can drop as low as 10%.
Even with relatively big batteries, if such generation levels continue for multiple days, you will soon run out of power.
A solar off-grid and backup system would need to be three or four times larger than a grid-tied system that uses Eskom as a backup when the sun doesn’t shine for extended periods.
Alternatively, you could use a generator to fill batteries, but this would also come at a high cost due to fuel prices.
Having access to Eskom’s grid provides additional redundancy should your batteries run empty or your PV generation not be sufficient to supply demand.
In addition, an Eskom connection can provide peak power of up to 13kW in average households, meaning you can easily run multiple power-hungry appliances such as stoves, kettles, geysers, washing machines, and pumps without the power tripping.
Cost-effective inverters typically only go up to 8kW of output capacity.
Hattingh provided specifications and pricing for various grid-tied systems that would require 5% or less Eskom power annually.
His estimates showed a system capable of producing 95% of the 600kWh monthly usage of a small household would start at around R138,000.
The price increases to R197,000 for households with 900kWh monthly usage and about R242,000 for 1,200kWh of consumption.
PV solar panels can produce copious amounts of electricity, but this can go to waste without sufficient battery storage, which can be expensive. Their performance is also highly susceptible to weather conditions.
Aside from panels, inverters, and batteries with much larger capacities, he also recommended a fuel-based generator priced from around R15,000.
The table below compares the specifications and prices of high-capacity grid-tied and off-grid backup power systems from AWPower and Rubicon.
It should be noted these prices are estimates.
If you are shopping around, check out our solar calculator here: https://www.awpower.co.za/solar-power-calculator/
| Grid-tried vs off-grid costs | ||
| Component | Grid-tied | Off-grid |
| 600kWh monthly (20kWh per day) | ||
| PV panel capacity | 4.14kWp JA Solar or Canadian Solar | 8kWp JA Solar or Canadian Solar |
| Inverter | 5kW DEYE Hybrid Inverter | 8kW Apex Oasis bidirectional inverter |
| Battery capacity | 5.12kWh Revov R100 7.4kWh SolarMD Advanced | 40kWh Freedom Won or WECO |
| Generator | No | Yes |
| Eskom annual power usage | 5% | 0% |
| Price | R138,481 — R152,124 | R437,000 |
| 900kWh monthly (30kWh per day) | ||
| PV panel capacity | 6.44kWp JA Solar or Canadian Solar | 8kWp JA Solar or Canadian Solar |
| Inverter | 5kW DEYE Hybrid Inverter | 10kW Apex Oasis bidirectional inverter |
| Battery capacity | 10.24kWh Revov R100 (2 x 5.12kWh) 14kWh SolarMD Advanced | 80KWh Freedom Won or WECO |
| Generator | No | Yes |
| Eskom annual power usage | 2% | 0% |
| Price | R196,977 — R207,439 | R618,000 |
| 1,200kWh monthly (40kWh per day) | ||
| PV panel capacity | 8.28kWp JA Solar or Canadian Solar | 11kWp JA Solar or Canadian Solar |
| Inverter | 8kW DEYE Hybrid Inverter | 10kW Apex Oasis bidirectional inverter |
| Battery capacity | 14kWh SolarMD Advanced or 15.36kWh Revov R100 | 80kW Freedom Won or WECO |
| Generator | No | Yes |
| Eskom annual power usage | 5% | 0% |
| Price | R241,713 — R257,529 | R836,000 |
**This article was first published on MyBroadband and can be accessed here: https://mybroadband.co.za/news/energy/442038-solar-power-with-eskom-grid-backup-vs-going-off-grid-surprising-price-difference.html