After years of installing off-grid solar systems, we can define what a typical off-grid setup in the Ballarat area looks like. While it might be tempting to simplify the answer to a 12kW system, the reality is more complex. It’s essential to consider three main components in the system design. The first and most crucial of these is the solar panels, which generate power and are the least expensive part of the system.
The calculation of the solar panel array is no longer strictly based on solar data or energy consumption; it’s now driven by the available roof space on sheds or other structures. While we can suggest that the panel array should be no less than 2-3kW per person in the household, the general rule is that the bigger the array, the better. In practice, we now typically install solar panel arrays ranging from 12kW to 15kW on most common sheds built around Ballarat.
One interesting point is that the difference in price between a 12kW and a 15kW system is very negligible, often only around $500. This is because larger arrays attract more STCs (Small-scale Technology Certificates), making the larger system more cost-effective.
The next component is the inverter, which determines how much power the house can draw from the system at any given time. Here, it’s straightforward: we almost always install a 12kW inverter, as it suits most homes. To put it in perspective, a typical grid connection provides around 40A, which is approximately 9kW. This means that a 12kW inverter not only meets but exceeds the typical grid-supplied power, ensuring that the house can comfortably handle its energy demands.
Finally, we come to the battery, which is where a significant portion of the investment goes. We typically end up installing a 20kWh battery, and the reason for this is that the battery volume needed must be capable of providing 12kW of power to match the 12kW inverter. This capacity is well-aligned with the average 24-hour energy consumption of a typical Australian household, making it a suitable and efficient choice for off-grid living.
Now, we can conclude that this is a very typical system for Ballarat and, I would say, for the whole of Victoria: a 12-15kW solar panel array, a 12kW inverter, and a 20kWh battery bank. The typical cost of this system is around $35k.