Currently with Eskom load shedding being a regular occurrence, we get a lot of calls from customers wanting to go Off-Grid. Going completely off-grid is expensive, and can cost anything from R200 000 to R500 000 depending on individual requirements. The cost per kWh for an off-grid system is also more than what most people pay for their electricity. However, if you really want to, it can be done. But it is not something we can sell “Off the shelf” and we do not quote on systems like this unless we have had extensive discussions to confirm requirements and expectations.
Ideally, one should first log the actual power consumption, for at least a week, to get an idea how how much power is used, the peaks, the average, and most importantly when the power is used, during the daytime or at night, as this will impact the system design. Logging can be arranged for R950 ex vat, to come install the loggers, remove them a week later, and analyse the data.
Most people, like myself, want to save money. And the only way to do this, is with a Grid Tied solar system, with no batteries. See our example of a Grid Tied solar system for a more detailed explanation. But basically, the aim is to cover your daytime consumption as much as possible, using solar. Things like pool pumps, fishponds, geysers, boreholes etc should all be put on timers, and be made to run sequentially throughout the day, to use up as much of the solar power as possible. The trick here is to no put too much or too little solar, because it is on the basis of “Use it or loose it” since most municipalities do NOT allow you to feed excess power back into the grid, and therefore it needs to be throttled and wasted if you do not use it. A common size for a grid tied system is around 2-4kW, with prices ranging from R34000 ex vat for a 2kW system, to R85000 ex vat for a 5kW system, using top quality solar modules and SMA Solar Inverters. An additional SMA Home manager 2 is required if you need to limit feeding into the grid, at a cost or approx R11500 ex vat.
BUT, at the same time, we also would like some backup during load shedding, and here is where I advise customers to minimise their backup requirements to as small as possible, to keep battery and inverter costs down. We use Victron Multiplus or Quattro inverters for smaller systems, and SMA Sunny Island’s for larger systems, and these can range from R30000 ex vat to R150000 ex vat depending on the size of the system. Quite a lot of work is required in the DB in order to seperate critical from non critical circuits, install additional earth leakages as required, install proper earthing to ensure safety during off-grid operation, and we use qualified electrician’s to do this work over and above the installation of the system itself. This is an additional cost, and can vary between R5000 ex vat to R25000 ex vat, depending on what changes need to be done in the DB board, and the complexity of the house wiring.
The Grid Tied solar system and the backup system, can be made to work together, to form a fully operational off grid system, so that if a power failure happens during the day, you have the added benefit of your solar panels assisting the batteries. At night of course, you are only running off the batteries, and together we need to agree on how many batteries you require to run a particular load, for a specific period of time.
So to close, there is no “One size fits all” when it comes to backup systems. But if your requirements and budget are in the same ballpark, then it is best if we sit down and discuss what system would work best for you.
We have two systems at BushPower, online stats below:
1. Our Grid Tied solar system, comprising 3 SMA Sunnyboy inverters, each on it’s own phase.
2. Our small backup system, comprising a Victron 2000VA Multiplus, linked to an SMA Sunnyboy 1.5, just to keep the office and lights on.