Giving Eskom the boot will cost you two to three times more than having a grid-tied solar and backup system that can provide over 90% of your electricity needs.
MyBroadband recently spoke to two established solar companies in South Africa — AWPower and Solar Advice — to learn more about the realities of going off-grid, in light of South Africans’ growing frustration about the severity of load-shedding in the past few months.
AWPower managing director Christiaan Hattingh said those looking to make a total switch must be honest with themselves about the real reason.
“Is it because you want to give Eskom the proverbial middle finger, or is it because you just really don’t have a reliable electricity supply in your area?”
Hattingh said the major issue with going off-grid using only a solar and battery backup system is that its performance can decline greatly during cloudy weather.
He said a good illustration of the problem was a recent bout of early winter rain and cloudy weather in Cape Town that drastically reduced home solar generation to levels typically only experienced mid-winter.
That meant customers had to rely more on the grid than usual.
Solar Advice marketing manager Sam Berrow said that increasing the size of your array by adding a few more panels could help get you through poor weather conditions.
“Adding to your battery bank will also ensure you use produced and stored solar power,” Berrow said.
Nevertheless, the company also discouraged customers from going totally off-grid.
“We usually recommend that our clients not disconnect from the grid completely. Instead, keep it as a backup power source,” Berrow said.
Hattingh explained that an entirely off-grid system came at a much greater cost than a large grid-tied system.
It needs to be capable of providing sufficient electricity for the worst month in terms of solar production in your area.
Therefore, Hattingh advised that customers instead look at designing systems that will supply 90–95% of their electricity requirements while remaining grid-tied.
“That 5–10% makes your system cost double or potentially triple,” Hattingh stated.
He explained that users who could drastically adapt their consumption habits might be able to avoid the additional cost while going off-grid.
However, this would require lowering or stopping the use of appliances like electric heaters and geysers, particularly when no solar power is produced.
Another way to address the periods of lower solar generation is to supplement your supply with a fuel-based generator that can provide dispatchable power.
Aside from the noise pollution and regular maintenance, a significant downside to this is that generating electricity with your own petrol or diesel will be significantly more expensive than simply using Eskom’s feed.
The savings you make from generating your own electricity could be offset by choosing to go completely off-grid — a case of cutting off your nose to spite your face.
Hattingh said smaller households that consume about 600kWh in a month could get a system comprising a 5kW inverter, 5kWh of battery storage, and solar panels with around 4kWp capacity.
That should provide an average of 500kWh of electricity per month and cost between R140,000 and R160,000.
However, he would recommend adding another 5kWh of battery capacity to ensure enough stored energy for night-time use.
That should cost in the region of R25,000, bringing the total cost to between R165,000 and R185,000.
Berrow provided MyBroadband with specifications for near-off-grid systems suited to households with respective average monthly consumption of 600kWh, 900kWh, and 1,200kWh.
The entry-level system would cost between R125,000 and R140,000 but could potentially cut the customer’s annual electricity bill by 81% with eight solar panels or 99% with ten panels.
Although the energy offsets could be higher than 100% when measured over the entire year, some of this energy will be wasted due to the limited battery capacity, unless you are able to feed it back into the grid.
While an energy offset above 100% also means you will generate more electricity throughout the year than you will consume in total, it does not mean you will necessarily be able to supply your full needs every month.
The table below provides a breakdown of the possible system configurations recommended by Solar Advice.
We have also added a 10kW petrol generator as a possible solution for those who really want to go off-grid and would find this to be a suitable backup.
A generator can also provide more output capacity for periods during which you might need to run appliances that will put your consumption over the capacity of your inverter.
Note that there might be additional costs involved with connecting a generator to your home’s electricity network using a qualified electrician.
|Solar Advice off-grid systems|
|Solar panel array||8–10 x 455W Mono Solar panels||12–4 x 455W Mono Solar Panels||16–20 x 455W Mono Solar Panels|
|Inverter||1 x Deye 5kW Hybrid Inverter||1 x Deye 5kW Hybrid Inverter||2 x Deye 5kW Hybrid Inverters|
|Battery/-ies||1 x 5.12kWh Dyness Battery||2 x 5.12kWh Dyness Battery||2 x 5.12kWh Dyness Battery|
|Annual energy offset||8 panels: 101%
10 panels: 126%
|12 panels: 101%
14 panels: 117%
|16 panels: 101%
20 panels: 126%
|Annual estimated bill savings||8 panels: 81%
10 panels: 99%
|12 panels: 81%
14 panels: 94%
|16 panels: 81%
20 panels: 99%
|Average daily battery backup time||6 hours||8 hours||6 hours|
|Estimated cost, including installation||R125,000–R140,000||R177,000–R191,000||R233,00–R254,000|
|Ryobi 10kW backup petrol generator||R49,999|
This content was originally published here.