In a note in November 2016 we analysed the economics of one of these batteries plus 5kW of rooftop solar plus grid for back-up and exports, relative to grid-only supply for a household with north facing roof in Adelaide that consumes 4800 kWh per year.
The comparison worked out the annual bill with and without PV and battery.
We assumed a 10 year battery life, 20 year PV life with no residual for either and assuming the household financed it with a household mortgage.
For grid offers we took the average of all 76 market offers from the 14 retailers making offers in the market, assuming in the first case that all discounts in those offers were achieved and in the second case assuming only that the unconditional discounts were achieved.
The results of the analysis are shown in Chart 1 below, which shows that for these assumptions, households are typically better off installing 5 kW solar and a battery rather than relying on grid only supply.