General GNX News, page-1115

The Bouldercombe battery will be primarily for FCAS (plus some opportunity for arbitrage). It is not for peak shaving/time shifting.

Not sure what you mean by "PHS does not have cycle cost" - PHS round-trip efficiency is likely somewhere between 70% and 80% (probably closer to 80% for Kidston due to the close proximity of the upper and lower reservoirs). Lithium grid scale battery round-trip efficiency (AC-AC) will likely be between 85% and 90%.