Graham,
if the grid goes down my PV shuts down as it need to know the Hz of the mains to feed to it.
If you add batteries & store power I understood you would not get the Feed in Tariff payment from the energy provider.
So I have switch that put excess power into heating the hot water & when that is done it feeds the grid.
This time of year we talk 1-2 kWhr per day only. Summer can see 25 kWhr.
My 3kW array is rated at 3064kWhr p.a. YTD 2016 we are at 3225. Best achieved was 3335 & the worst 3084.
