I currently have a farm shed with 55 x 180W REC panels on it feeding 2x SMC5000TL inverters. Shed usage is absolute minimal so come the end of the GFIT the income from this system will be drastically reduced and hardly worth changing it all to net.
I am also in the process of building a new house which will be off grid, so my plan was to move around 5kW of the panels plus one inverter to the new dwelling early next year. I will then buy a Sunny Island and a battery system.
Current household usage is around 14kWh/day (separate from the "solar shed" mentioned above)but this will reduce to maybe 11kWh/day because I will not be running a pool pump. The 10KW shed system over the last 6 years has produced a min. of 16kW per day and a max. of 57 kW/day.(average over a month) so presumably a 5kW system will produce half that.
So, my question is what size battery will I need?
I note that the LG Chem battery off ebay is about 6.4 kWh expandable to 9.6 and 12.8.
It looks to me as if say 5.5kW (half the 11kWh) consumed over a 12 hr period without any additional input would be beyond the capability of a single 6.4 kWh battery. Correct????
What is the normal factor for calculating battery storage capacity required?
My consumption may be a little higher than usual because I am running 2 fridges and a freezer. This will not change in the new house. By my calcs those 3 items alone use about 3.75 kWh /day. Not sure where the other 10.25 kWh goes to.