I wont argue to much about the use of 'excess power' to pump...

I wont argue to much about the use of 'excess power' to pump water,but would some of that excess power come from batteries?Batteries have a tendency to run flat. 
Just to be a bit of a smart A,Those batteries that pay them selves off in 2 to 3 years,are they the same batteries that need to be replaced every 10 years (currently).
I'll agree with yr comments re coal v gas plants ,but i'll add  cheap energy built Australia ie re coal,we can't just subsidise solar/wind which rely on battery storage and reduce the efficiency of coal plants and replace cheap base load coal hele plants until we have the technology to provide cheap base load energy alternatives.
Batteries imo don't make common sense,dams to capture water for irrigation etc combined with non pumped hydro electricity production makes sense,and imo lol and u know who,nuclear will be the future for major energy requirements as it continues to be developed,lol i refer to star trek.
Anyway ,tls's energy requirements are a very serious issue,and they should invest in that tassy hydro non pumped plant and the power cables connecting it to the mainland grid.
As posted last 2 years tls electricity bill 'increased' $200m,and thats before the roll out of 5g..