Frequently Asked Questions
In the course of doing my installation, I’ve been asked a number of questions regarding the process. These are a few of the most common questions that have come up.
Feel free to drop me a line if you’d like some additional info on any any of the topics discussed here.
The point is to look at your requirements, short and long term, before making a decision. It could start getting very expensive if you don’t do your homework properly from the start/
Not only with this save you some money on your utility bill, you’ll also save money on your inverter system as you’ll need less to power more.
An example, we’ve all got low voltage downlights in our homes. These little buggers consume 50W each! Replace these with 5W LED lamps and you’ve reduced your lighting loads by 90%.
As a real life example, I had a combination of 50W/12V downlights (20 x 50W) and fittings with 60W candle lamps (12 x 60W). This was a total consumption of around 1,720W! These are the lights that are on the most, probably around 6-hours/day on average.
I replaced the 50W downlights with 5W LED lamps and the candle lamps with 4W LED candle equivalents. The consumption is now around 148W for the same fittings. This is a saving of 1,572W. Over 6-hours this equates to 9.4kWh per day, 282kWh per month. Most importantly, at the mid-range scale of the utility cost, this amounts to a saving of R450 a month on my electricity bill.
That’s a simple and relatively inexpensive way to reduce consumption. Next on the list would be water heating.
Using solar water heating can reduce your consumption by another 30%.
Changing over to gas for cooking can further reduce your electrical requirements. You’ll save a bit of money here, but the real objective is to reduce electrical energy consumption.
By doing this, the size of the inverter system can be drastically reduced while giving you a lot more flexibility in planning.
If it’s just there for a small back-up system for periods of loadshedding, you could get away with 2 x 102Ah High Cycle batteries. These could easily power a TV and some LED lights for 2 to 3 hours.
For your average system that can power most of an average house, you could get away with a 48V 200Ah battery bank.
I upgraded my system to 260Ah and have managed to run my TV, decoder, PC, router, most lights in the house and garage, some chargers and other small loads for 4-hours and only used 20% of the battery capacity.
If the batteries are going to be used frequently, it’s worth it to spend a bit more on decent batteries that are going to last for at least 5 to 6 years.
A each system will be unique to some degree, the requirements will vary. I’ll give a list of the essential components.
- Supply circuit breaker. This should be sized according to the inverter rating and manufacturer’s recommendations. In my case, with the 5kVA inverter, this is a 50A circuit breaker connected BEFORE the main earth leakage unit.
- If your current main switch is an earth leakage unit, then you will need a new double pole main switch (typically a 63A circuit breaker for most domestic installations).
- Cabling from the inverter supply to the inverter. This should be sized according to the supply breaker. For a 50A supply, you would need a 10mm2 cable.
- Local isolator for the inverter if the inverter is installed remote from the point of supply. This should be a double pole isolator to switch both live and neutral supplies.
- Cabling from the local isolator to the inverter (if required as per previous point).
- Cabling from the inverter to your sub-distribution board, or back to your existing main DB. This depends on your configuration. I prefer having a separate DB for the inverter loads and moving the existing circuits to this panel rather than feeding back to the existing board. It’s a LOT safer as there is only one supply into the board.
- For the new DB you will need a main switch. This can be an earth leakage device or a double pole circuit breaker.
- If the main switch is a circuit breaker, you will need an earth leakage device to feed your plug circuits. If you don’t use an earth leakage device, all socket outlets will need to be replaced with the red dedicated type with D type earth-pin. I suggest adding the earth leakage and leaving your socket outlets alone.
- Circuit breakers for the new sub-DB, or you can use the breakers you already have in your existing DB.
- Indicator lamp on the DB that is fed from the inverter to indicate when the feed from the inverter is live. This isn’t just because it looks nice, it;s a legal requirement.
- Battery link cables to connect your battery bank. These should be sized according to the maximum load of the inverter. In my case the maximum inverter output is 4000W, so then the load would be 4000W/48V = 83A. I used 25mm2 welding cable that is rated just over 100A. Try keep the interlinking cables as short as possible.
- Cables from the battery bank to the inverter should be sized the same way and also kept as short as possible.
- A fuse or DC circuit breaker is also required between the battery bank and inverter. Is a minimum, you could use a single fuse on the positive battery feed as this is the cheapest method. Just remember to use proper fuses and fuse holders. Automotive type fuses are not the right way to go. DC circuit breakers rated above 63A get fairly pricey, but make for a better installation.
- If you’re looking at using solar energy as well, then the shopping list grows quite a bit: solar panels, solar panel mounting kit, solar cable, PV string combiner, fuses, surge protection, etc. This will all be determined by the type of system you want to set up.
- Optional extras would be things like energy meters, external battery monitors, remote displays, voltmeters, etc., etc. These are really just nice to have and won’t affect the operation of your system at all.
Here’s a list of links to some suppliers of the various pieces of equipment:
Electrical equipment and wiring:
The above list is by no means comprehensive, but you should be able to get most of what you need from the above suppliers at very competitive prices.
There is a wealth of knowledge and information available online (hopefully this is one of those places) that can help you through your installation.
You will need to have your installation tested and certified by a qualified and registered electrician who can give you a Certificate of Compliance (CoC) for your installation.
I believe it is possible to get an average home almost completely off-grid for around R165,000.
This would include the following:
- 5kVA inverter (R15,000)
- 3kW of solar panels (R30,000)
- 500Ah battery bank (R40,000)
- Solar water heating system (R25,000)
- Gas stove including gas installation (R10,000)
- Solar pool pump including panels and cabling (R30,000)
- Electrical installation (R15,000)
If you go partially off-grid the costs can come down drastically.
By this I mean downgrading the battery bank to around 200Ah to provide standby only for loadshedding.
The solar panels could be reduced to just cater for the daytime loads and a bit of battery charging as required. Run the pool pump during periods when there is capacity available. If there is washing done in the morning, this will need to dry before the ironing starts. Use this gap to run the pump off solar.
A system like this would be more in the region of R110,000.
If you’ve already got gas for cooking and solar water heating, you’re off to a good start and your cost can come down to R55,000.
The cost is still high, but you will be saving on your utility bill every month.
A system of R40,000 without solar input will give you peace of mind knowing that you won’t be affected by loadshedding and life can carry on as normal.
This is an expensive solution though and has absolutely no return on your investment, but if it’s put together properly from the start, it’s a great starting point for going off-grid.