AD Australia reaches record 36.8 pct renewables in 22/23, lowest coal this century, page-39

From the SMH, in a very disparaging article:

For every 100 units of electricity purchased from the NEM to pump water uphill, only 75 units are returned when the water flows back down through the turbine generators.

Alternators may have an efficiency over 90%, I'm talking about the furnace/boiler/turbine/alternator chain.

"he efficiency is dictated by the parameters of this thermodynamic cycle. The overall coal plant efficiency ranges from 32 % to 42 %"

As to your claim that there will never be excess Solar and Wind, there isn't now but could be in the future (after my ahole is pointing horizontal)

Having said all that, SH2 does not look too flash given its blowouts of cost and time to build and the devastation on the Snowy Nat Park