That’s it, I’m going off grid!

How it starts: 

It’s 19:36 on a Thursday evening in a suburb in South Africa. Power in the area has been off since the morning (some think it’s disguised loadshedding) and residents without back up are fuming. Life in South Africa (and anywhere) can be tough at the moment, but this is the additional mental load that the average citizen is no longer willing to tolerate. 

“That’s it, I’m going off the grid! I have no trust in Eskom anymore”, bemoans the citizen. 

We thought of sharing some insights into what that statement actually means in terms of cost for the average household. Pricing on solar components has dramatically dropped over the past year and so the good news is that it’s becoming cheaper to achieve this objective. It should also be noted that in our calculations we’ll reference Victron product as it’s what we believe in due to the transformer based technology. If this is going to become your main source of power, you need the equipment to be reliable and last. 

Inverter sizing:

Firstly, and this is well publicised, it all starts with the inverter. Your inverter size essentially decides the capacity your off-grid system can produce without grid (i.e Eskom/municipality). Inverters differ in size but a 5kVA inverter should typically run essentials on the average 3-4 bedroom household. High consuming appliances like geysers, ovens, aircons should not be connected to these inverters, unless they are the more ecofriendly consumption units and don’t draw heavy loads or generate high indicative loads on start-up. If the average household would like to include the geyser(s), aircon(s), pool pump, oven etc, it would be wiser to look at an 8kVA inverter and upward depending on the amount of these appliances you wish to connect. 5kVA Victron inverters with Cerbo GX & MPPT will typically come to around R28k Incl. Vat. 

Battery Sizing: 

The next major component is your battery. We always recommend that your battery size is the same size as your inverter capacity as a minimum. i.e. 5kVA Inverter = 5Kwh battery. If we work on essential appliances such as lights, WI-FI, TV, computers, fridges, maybe a microwave or air fryer for short periods consume 200w/h – 500w/h on average (depending on how many you use at the same time), the 5kWh battery will give you roughly 8-10 hours of back up without needing to charge. Typically a battery will discharge to about 10% - 15%state of charge before going into protection mode and cutting power. A quality Freedom Won5Kwh Lithium Ion battery (don’t waste time on lead acid) will cost you around R25k Incl. Vat. Remember that you get what you pay for in terms of the battery management system (BMS) which is crucial to longevity and performance of your battery. The BMS helps to balance your cells and prolong the efficiency. This type of battery carries a 10 year warranty or 4 000 cycles where a cycle is measured as discharge to below 50% and recharge back up to 100%. 

How many solar panels? 

Finally, the most final component in becoming self-sufficient is your photovoltaic panels (PV) that generate energy from the sun. It all depends on the size of panel that will fit onto your roof best, but 455w – 550w panels are the most popular. These can range from R1.5k Incl. Vat per panel to R3.0k Incl. Vat. When sizing the amount of panels, it’s key to understand your average daily consumption (during sunlight hours) and what additional power you may need to charge your battery(s). i.e. House uses 1kWh on average during daytime, plus a 5kWh battery needs to charge, so 6 x 550w (3.3KWp) panels would be a suggested minimum.  Obviously the more the consumption & bigger the battery storage, the more panels required. Sometimes roof space may not be sufficient which leads to car port structures housing additional panels which can increase the cost. 

Do I still need a generator? 

Yes, if you are planning to go off grid, it would be wise to have a back up in case your batteries run out of capacity or not enough PV can be generated for whatever reason. In this example a 5.5kWh generator would suffice and you can pick up many second hand units on the market as more people go solar.

So, what would it cost to go off grid on your energy requirements if you had a 5kVA inverter and your average consumption is 1kWh? Here is a rough example…